Neuroblastoma: Clinical Guidelines

List of Abbreviations

BP – blood pressure

ACS – abdominal compartment syndrome

aPTT - activated partial thromboplastin time

EFS – event-free survival

BAL – bronchoalveolar lavage

HDCT – high-dose polychemotherapy

WHO – World Health Organization

G-CSF – Granulocyte colony-stimulating factor

GN – ganglioneuroma

GM – galactomannan

GNB – ganglioneuroblastoma

DWI – diffusion-weighted imaging

DIC – disseminated intravascular coagulation

EBRT – external beam radiotherapy

DNA – deoxyribonucleic acid

ZNO – malignant neoplasms

LTS – life-threatening symptoms

GI – gastrointestinal tract

IMV – invasive mechanical ventilation

ELISA – enzyme-linked immunosorbent assay

PPI – proton pump inhibitor

CLABSI – central line-associated bloodstream infections

CT – computed tomography

CE – contrast enhancement

CF – conversion factor.

ABG – acid-base balance

123I-MIBG – meta-iodobenzylguanidine [123I]

MRI – magnetic resonance imaging

INR – international normalized ratio

MRSA – methicillin-resistant Staphylococcus aureus

NB – neuroblastoma

NSE – neuron-specific enolase

NSAIDs – nonsteroidal anti-inflammatory drugs

OS – overall survival

OMS – opsoclonus-myoclonus syndrome

SPECT – single-photon emission computed tomography

VGPR — very good partial response

PVC – peripheral venous catheter

CR — complete response

PCT – polychemotherapy

PCR – polymerase chain reaction

PN – parenteral nutrition

SFD – single focal dose

RF – Russian Federation

RP – radiopharmaceutical

TFD – total focal dose

SNS – sympathetic nervous system

MODS – multiple organ dysfunction syndrome

SCT – spiral computed tomography

HSCT – hematopoietic stem cell transplantation

TEE – total energy expenditure

PONV – postoperative nausea and vomiting

CVC – central venous catheter

CVP – central venous pressure

CNS – central nervous system

US – ultrasound examination

FN – febrile neutropenia

CT – chemotherapy

CE – cephalosporins

ALP – alkaline phosphatase

EchoCG – echocardiography

EC – epidural compression

REE – resting energy expenditure

EN – enteral nutrition

ANTT – Aseptic Non-Touch Technique

ASCO  – American Society of Clinical Oncology

BuMel – busulfan/melphalan conditioning regimen

CEM – carboplatin/etoposide/melphalan conditioning regimen

CTV – clinical target volume

COG  – Children Oncology Group

del1p – 1p deletion

FISH – in situ fluorescence hybridization

GTV – gross tumor volume

IDRF – Image Defined Risk Factors

imb1p – 1p imbalance

IMRT – Intensity-Modulated Radiation Therapy

INRGSS – International Neuroblastoma Risk Group Staging System

MLPA – multiplex ligation-dependent probe amplification

NSS – International Neuroblastoma Staging System

PTV – planning target volume

TreoMel – treosulfan/melphalan conditioning regimen

VMAT – VoluMetric Arc Therapy

Terms and Definitions

Overall survival (OS) is defined as the time from the date of NB diagnosis until patient death from any cause or the last patient follow-up.

Event-free survival (EFS) is defined as the time from the date of NB diagnosis to an adverse event, which is understood as progression, relapse (in case of achieving a complete response), development of a secondary malignant tumor, death from any cause, or the date of the last patient follow-up.

Disease progression is defined as the appearance of any new tumor lesion; an increase of > 25% in any pre-existing measurable lesion; detection of bone marrow involvement by NB cells if the bone marrow was previously uninvolved.

Disease relapse is defined as the appearance of any new tumor lesions in patients who previously achieved complete response (CR) according to the response evaluation criteria for patients with NB.

It should be noted that the definition of events differs in patients of the observation group.

In patients of the observation group, relapse/progression refers to the following situations:

• in stages 1–3: appearance of distant metastases;

• in stage 4S: progression of bone marrow involvement, where the number of tumor cells exceeded 10% of nucleated cells, and/or the appearance of metastases in organs other than liver and skin involvement (so-called transformation to stage 4);

• local progression of the primary tumor (in stages 1–3) or progression of organomegaly (in stage 4S) leading to the development of LTS.

Regression is defined as:

• no change: changes do not meet the criteria for progression, regression < 10% in all planes;

• minimal regression: regression of the primary tumor ≥ 10% and < 25% in one or more planes and < 10% when assessed in other planes according to ultrasound, MRI, or CT data (the previous study must be available to confirm regression);

• definite regression: regression of ≥ 25% in one or more projections and < 25% when evaluated in other projections according to ultrasound, MRI, or CT;

• complete regression: absence of residual primary tumor detectable by imaging methods (corresponds to the definition of complete response according to the INSS criteria).

Primary resistance is defined as:

Primary resistance is established based on an evaluation performed at an interim stage of induction therapy (no later than the 4th course of induction therapy) or upon its completion (after the 6th course of induction therapy) for high-risk patients. Resistance is considered to be less than a partial response to prior therapy (excluding progression). Neutropenia is defined as a granulocyte count of less than 0.5×10⁹/L, or less than 1.0×10⁹/L with an expected decrease over the next several days.

Fever – a single body temperature elevation ≥ 38.3°C or a body temperature ≥ 37.8°C persisting for one hour or more.

Hypothermia – a decrease in body temperature below 36°C. This parameter is an important indicator of an infectious process, especially in young children and patients receiving glucocorticosteroids.

Fever of unknown origin – a condition characterized by fever in the absence of clinical and radiological manifestations of infection and microbiological data.

Bacteremia – identification of a microorganism from a blood culture taken during a febrile episode that is not a contaminant. False bacteremia refers to the identification of so-called contaminating microorganisms—skin commensals of the hands (coagulase-negative staphylococci, Propionibacterium spp., Micrococcus spp., etc.)—in the case of their single identification.

Proven infection is defined by the identification of a microorganism from sterile body substrates (blood, cerebrospinal fluid, urine, biopsy material) in the presence of symptoms of an inflammatory response, or the isolation of a pathogen from non-sterile substrates (skin, mucous membranes, gastrointestinal tract) with a corresponding local clinical presentation of infection.

Probable infection is defined without the identification of a microorganism from the investigated media and the presence of clinical and/or radiological signs of infection with a rapid response to anti-infective therapy.

Febrile neutropenia – a symptom complex combining the development of fever or hypothermia in a patient with criteria for neutropenia.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Neuroblastoma (NB) is a malignant tumor developing from precursor cells of the sympathetic nervous system (SNS). NB is the most common malignant extracranial solid tumor in childhood. NB accounts for 7–8% of all malignant neoplasms (MN) in children aged 0–14 years [1–3]. It is the most common solid tumor in infants and young children, with peak incidence occurring at 18 months, and 90% of cases diagnosed under the age of 10 years.

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

Most cases of neuroblastoma are considered sporadic; however, the possibility of tumor development in individuals with a genetic predisposition has been demonstrated, including familial forms of the disease and neuroblastoma arising in the setting of specific genetic syndromes. Early population-based studies aimed at assessing the contribution of genetic factors to the development of childhood malignancies showed that heredity is responsible for 1–2% of all neuroblastoma cases. However, in recent years, the widespread implementation of molecular genetic studies has allowed for a much better characterization of the genetic events contributing to neuroblastoma development, the identification of additional genetic syndromes characterized by an increased frequency of neuroblastoma, and a better characterization of familial cases of the disease [4].

The biological features of neuroblastoma represent one of the most important initial characteristics of the tumor influencing the prognosis of the disease [5]. The biological and clinical heterogeneity of neuroblastoma is based on genetic abnormalities that can be divided into two large groups: numerical chromosome abnormalities and segmental abnormalities. The latter are characteristic of tumors with an aggressive clinical course.

1.3 Epidemiology of the Disease or Condition

The incidence rate of neuroblastoma is 0.95–1.4 per 100,000 children aged 0–14 years, with the peak incidence occurring in infants in their first year of life. Neuroblastoma is the most common type of malignant neoplasm in infants in their first year of life, accounting for up to 28.6–35% of all cases in this age group [6–8].

The necessity of optimizing therapeutic approaches in patients with neuroblastoma is underscored by the fact that neuroblastoma occupies a disproportionately high position in the mortality structure of the pediatric population in developed countries, ranking 3rd and second only to leukemias and central nervous system (CNS) tumors. At the same time, the proportion of neuroblastoma in the mortality structure reaches up to 15% [6–8].

A differentiated approach to the treatment of patients with malignant neoplasms in general, and neuroblastoma in children in particular, is currently considered the standard of specialized medical care. This approach is based on the analysis of various clinical characteristics and biological features of the tumor that influence the course and prognosis of the disease, followed by the adaptation of the scope and intensity of anti-tumor therapy depending on the presence or absence of adverse prognostic factors. It should be noted that the main objective is to minimize the therapeutic impact in patients with favorable disease characteristics by reducing the number and cumulative doses of cytostatic drugs, decreasing the number of patients requiring radiotherapy (RT) and large-volume surgical interventions, and consequently lowering the risk of long-term therapy-related sequelae while maintaining high rates of event-free survival (EFS) and overall survival (OS). Conversely, in patients with a combination of adverse tumor characteristics, attempts are made to intensify therapy and incorporate new therapeutic options in order to neutralize the negative impact of the aforementioned factors on the disease prognosis.

1.4 Features of Coding the Disease or Condition

C38.2 – Malignant neoplasm of posterior mediastinum

C47.0 – Malignant neoplasm of peripheral nerves and autonomic nervous system of head,

face, and neck

C47.3 – Malignant neoplasm of peripheral nerves of thorax

C47.4 – Malignant neoplasm of peripheral nerves of abdomen

C47.5 – Malignant neoplasm of peripheral nerves of pelvis

C47.6 – Malignant neoplasm of peripheral nerves of trunk, unspecified

C47.8 – Malignant neoplasm of peripheral nerves and autonomic nervous system, overlapping

C47.9 – Malignant neoplasm of peripheral nerves and autonomic nervous system, unspecified site

C48.0 – Malignant neoplasm of retroperitoneum

C74.1 – Malignant neoplasm of medulla of adrenal gland

C74.9 – Malignant neoplasm of adrenal gland, unspecified

C76.0 – Malignant neoplasm of head, face, and neck

C76.1 – Malignant neoplasm of thorax

C76.2 – Malignant neoplasm of abdomen

C76.7 – Malignant neoplasm of other ill-defined sites

C76.8 – Malignant neoplasm of other and ill-defined sites, overlapping

D48.3 – Neoplasm of uncertain or unknown behavior of retroperitoneum

1.5 Classification of the disease or condition

Depending on the degree of differentiation, neuroblastoma, ganglioneuroblastoma (GNB), and ganglioneuroma (GN) are distinguished.

Therapy for patients with neuroblastoma is based on their classification into risk groups depending on a combination of prognostic factors, such as age at diagnosis, disease stage, molecular genetic characteristics of the tumor, including MYCN gene status and 1p deletion.

The assessment of disease dissemination in neuroblastoma is carried out within the framework of the International Neuroblastoma Staging System (INSS) [9]. It should be noted that the INSS is a postsurgical staging system (Table 1).

Table 1. International Neuroblastoma Staging System (INSS)

The disease stage in multifocal tumors (e.g., bilateral adrenal involvement) is assessed by the most severely affected side and designated by the letter M (e.g., 2_M).

In 2009, a new staging stratification system was published and implemented. It is based not on the extent of surgical resection, but on the identification of Image Defined Risk Factors (IDRF) determined by imaging methods (CT and MRI) — INRGSS (International Neuroblastoma Risk Group Staging System). IDRFs include tumor encasement of major vessels, nerve roots, the renal pedicle, and other factors that may limit the extent of surgery and predict surgical complications [10] (Table 2).

Table 2. Image Defined Risk Factors (IDRF) for neuroblastoma identified by imaging methods (CT and/or MRI) [10].

INRGSS is a preoperative staging system comprising four stages — L1, L2, M, and MS (Table 3).

Table 3. International Neuroblastoma Risk Group Staging System (INRGSS) [11].

1.6 Clinical presentation of the disease or condition

The clinical presentation of the disease is determined by the anatomical location of the primary tumor, the degree of invasion and compression of adjacent organs and tissues, as well as the anatomical location of metastases. The clinical presentation may vary from being asymptomatic — discovered incidentally during routine health checks or screening for another condition — to presenting with palpable abdominal tumor masses, abdominal distension, pain, cough, and dyspnea when the tumor is located in the mediastinum. When the tumor invades the spinal canal or compresses peripheral nerve trunks, neurological symptoms may develop, such as paresis, paralysis, pelvic organ dysfunction, limb edema, pain syndrome, and other manifestations [2].

In metastatic forms, the clinical presentation is determined by the localization of metastases, ranging from an incidental finding during imaging to the development of anemia syndrome due to bone marrow involvement, bone pain due to bone lesions, and visual impairment due to orbital metastases, up to complete blindness. Massive metastatic liver involvement may manifest as increased abdominal girth and hepatomegaly.

The clinical presentation of the disease may also be due to the presence and nature of a paraneoplastic syndrome.

Neuroblastoma is a tumor that, compared to other malignant neoplasms, is most frequently accompanied by the development of paraneoplastic syndromes.

Paraneoplastic syndromes in neuroblastoma include the following conditions: secretory diarrhea (primary and secondary), opsoclonus-myoclonus syndrome (OMS), constipation, arterial hypertension, and others.

Thus, in a number of patients, the production of vasoactive intestinal peptide leads to prolonged, refractory diarrhea accompanied by electrolyte disturbances.

Neuroblastoma is considered a highly immunogenic tumor characterized by the development of immune-mediated paraneoplastic syndromes. One of the most frequent paraneoplastic syndromes in neuroblastoma is OMS — opsoclonus-myoclonus syndrome. The incidence of OMS in neuroblastoma reaches 2–4%. OMS, also known as "dancing eyes syndrome" or "Kinsbourne encephalopathy," is characterized by three main manifestations: opsoclonus (conjugate rapid, irregular, and unequal eye movements, usually in the horizontal plane, most pronounced at the start of fixation), myoclonus (non-epileptic twitching affecting the trunk, limbs, and face), and ataxia. These symptoms are often associated with behavioral disturbances (e.g., irritability, tearfulness, up to manifestations of autoaggression and aggression towards parents), sleep disorders, and cognitive impairment [13].

2. Diagnostics, medical indications and contraindications for diagnostic methods

Diagnoses of neuroblastoma and ganglioneuroblastoma are established based on international criteria (Brodeur G.M., 1993), which include[12]:

• pathological examination of the primary tumor/metastasis/bone marrow trephine biopsy tissue using immunohistochemical methods;

  OR

• pathological examination of the primary tumor/metastasis/bone marrow trephine biopsy tissue (with or without immunohistochemical examination) and elevated levels of catecholamine metabolites in serum and/or urine;

  OR

• detection of neuroblastoma cells in bone marrow obtained by bone marrow aspiration and/or trephine biopsy, and elevated levels of catecholamine metabolites in serum and/or urine.

Comments:

If a histological diagnosis other than neuroblastoma, ganglioneuroblastoma, or ganglioneuroma is obtained, the patient should receive therapy in accordance with the clinical guidelines for that specific disease.

1. Diagnosis and management of patients under 6 months of age in good clinical condition with a localized adrenal mass.

Neonates or infants have a favorable prognosis even without specific treatment. Adrenal masses detected by standard ultrasound in an infant in the first year of life with a good clinical status can be either neuroblastoma or hemorrhage. Spontaneous regression is also a characteristic phenomenon of neuroblastoma. In this case, the initial workup may consist of two stages [13, 14].

• It is recommended to perform the following diagnostic workup [14] when an adrenal mass is detected in infants in the first 6 months of life:

• 1. Assessments required for all children under 6 months of age with a suspected adrenal mass:

• a. clinical status with a special focus on the skin, abdominal circumference, and liver span upon palpation;

• b. complete blood count: electrolytes, liver function tests (ALT, AST, GGT), kidney function tests (creatinine, urea, uric acid), and coagulation profile;

• c. tumor markers: LDH, ferritin, NSE, and if available, serum and urinary catecholamine metabolites (VMA, HVA);

• d. ultrasound of the neck, abdomen (evaluating the size of the adrenal mass as well as the size and structure of the liver to rule out metastatic involvement), pelvis, and brain;

• e. contrast-enhanced CT/MRI of the abdominopelvic cavity with IDFR description;

• f. 123-I-MIBG scintigraphy, if available.

GGR BLEL 3Grade of Recommendation B (Level of Evidence 3)

Comments: If an infant in the first 6 months of life has a localized adrenal mass measuring less than 3 cm for a solid structure and less than 5 cm for a cystic form, without compression of surrounding organs according to abdominopelvic ultrasound / contrast-enhanced abdominopelvic CT / contrast-enhanced abdominopelvic MRI; with no evidence of metastatic disease based on physical examination and imaging (ultrasound/CT/MRI); stage L1 according to INRGSS; and with a satisfactory general somatic status, the patient may be managed with active surveillance for 12 months from the detection of the mass. This includes regular evaluation of the general condition by a pediatric oncologist and pediatrician, abdominopelvic ultrasound (at least once every 2 weeks), assessment of tumor markers (NSE, LDH) (at least once every 2–3 months), urinary catecholamine metabolites (HVA and VMA) (at least once every 2–3 months), and contrast-enhanced abdominopelvic CT / contrast-enhanced abdominopelvic MRI (every 3 months or earlier if negative dynamics are detected on abdominopelvic ultrasound and/or clinical symptoms appear). A contrast-enhanced abdominopelvic CT / contrast-enhanced abdominopelvic MRI is also indicated 12 months after the detection of the adrenal mass or earlier if clinical symptoms appear, tumor marker levels (NSE, ferritin, LDH, urinary catecholamine metabolites [HVA and VMA]) increase, the mass enlarges on abdominopelvic ultrasound, metastatic spread is suspected, or a mass develops in the contralateral adrenal gland, in order to determine the indications for surgical treatment.

If bilateral adrenal involvement or metastatic spread is suspected, a complete workup as specified in the "Diagnostics" section is indicated.

In the presence of clinical symptoms such as arterial hypertension and/or precocious puberty, an evaluation must be performed to rule out other neuroendocrine tumors.

Assessments required if the tumor persists during the 12 months of active surveillance.

If the adrenal mass persists in a child during 12 months of active surveillance or if negative dynamics appear earlier, the full range of laboratory and imaging studies specified in the "Diagnostics" section should be performed, and the option of surgical resection should be considered.

In the event of complete regression of the adrenal mass, active surveillance should be continued in the following scope: abdominopelvic ultrasound and determination of tumor markers (NSE, LDH) at least once a year for a duration of at least 3 years.

If complete regression of the adrenal mass occurs, but elevated tumor marker levels persist, a complete workup is required.

Indications for surgical treatment:

Mass size ≥5 cm for the cystic form; ≥3 cm for a solid structure (refer to the maximum tumor dimension);

Stage L2 according to INRGSS;

Increase in tumor volume >50% during active surveillance;

Increase in urinary catecholamine metabolites (HVA and VMA) >50% that does not decrease to baseline levels within 12 weeks (if evaluation is available);

A mass persisting at 12 months of follow-up with a size >2 ml (diameter 1.6 cm), or any mass size in the case of elevated catecholamine metabolite levels. A reference review of control imaging at a national/federal center and a multidisciplinary discussion on the indications for surgical removal of the adrenal mass are required;

Suspicion of metastatic spread.

2.1 Complaints and Anamnesis

Clinical symptoms in neuroblastoma are determined by the anatomical location of the primary tumor and metastases. General symptoms (fatigue, decreased appetite, fever, sweating, etc.) are most commonly detected in widespread disease. When the tumor is located in the retroperitoneal space, the most frequent complaints are abdominal enlargement, pain, and bowel dysfunction (ranging from constipation to prolonged refractory diarrhea as a manifestation of paraneoplastic secretory diarrhea). When the tumor is located in the posterior mediastinum, symptoms include cough and dyspnea. Neurological symptoms, such as paresis and pelvic organ dysfunction, occur when the tumor extends into the spinal canal and epidural compression (EC) develops.

It is necessary to actively question the child/patient's parents about the presence of complaints and the time of their onset.

In some cases, neuroblastoma is detected during routine health screenings or workups for another disease (e.g., acute bronchitis).

• obstetric history,

• prior diseases,

• vaccination history,

• family history,

• clinical signs at the time of disease onset, disease dynamics, and therapeutic options prior to the neuroblastoma diagnosis.

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Comment: Genetic counseling and/or genetic testing is recommended in cases of:

• a positive family history of cancer (first-degree relatives diagnosed under the age of 45 years; 2 or more second-degree relatives diagnosed under the age of 45 years; 2 or more family members with malignancies across 3 generations at a pediatric age),

• consanguineous marriage,

• a patient with two malignancies (primary malignancies),

• congenital developmental anomalies in the patient,

• a multifocal tumor in the patient (more than one anatomical site of the primary lesion),

• detection of a potentially germline pathogenic variant during genetic analysis of tumor tissue.

2.2 Physical Examination

Comments:

The initial examination includes:

• anthropometric measurements (weight, height, and body surface area) and assessment of nutritional status (percentiles). Assessment for congenital malformations and dysmorphic features;

• assessment of skin and mucous membranes;

• assessment of cardiovascular system function;

• assessment of pulmonary system function;

• abdominal palpation, measurement of abdominal circumference, evaluation of liver and spleen size, and ruling out or confirming palpable abdominal masses;

• assessment of the size of peripheral lymph nodes;

• characterization of pelvic organ function;

• assessment of motor activity.

2.3 Laboratory Diagnostics

Comments: these tests are also performed prior to starting chemotherapy courses that include nephrotoxic drugs.

Comment: it is advisable to assess tubular function before starting polychemotherapy and subsequently use the baseline values to rule out tubular injury in patients receiving #ifosfamide** therapy.

Tumor markers:

Comment: the result depends on the patient's age and the assay used to determine the parameter. "Normal" or "elevated" values are defined in accordance with the reference ranges of the laboratory where the measurement is performed.

Comment: NSE levels are affected by hemolysis and degradation at room temperature. Therefore, a non-hemolyzed blood sample must be analyzed within 2–6 hours in the local laboratory. If the sample is sent to another laboratory, only serum must be used. The result depends on the patient's age and the assay used. "Normal" or "elevated" values are defined in accordance with the reference ranges of the laboratory where the measurement is performed.

Comments: if the result is normalized to creatinine concentration, there is no need to collect 24-hour urine. "Normal" or "elevated" values are defined in accordance with the reference ranges of the laboratory where the measurement is performed.

This test is performed depending on the availability of the method. HVA and VMA levels are assessed initially, during therapy, and at follow-up monitoring stages.

2.4 Instrumental Diagnostics

Comments: recommended timing for audiological testing:

• Baseline testing prior to treatment initiation.

• After each course of polychemotherapy using cisplatin**. If sensorineural hearing loss caused by the ototoxic effect of platinum drugs is detected, discuss a potential change in the treatment regimen.

• 4–6 weeks after completion of treatment (last administration of cisplatin**, #carboplatin**).

• Annually after completion of specific therapy.

Main hearing test methods to detect hearing loss caused by the ototoxic effects of medications:

• Pure-tone audiometry in standard and extended high-frequency ranges up to 16-20 kHz (the method for determining hearing thresholds depends on the child's age and developmental level: visual reinforcement audiometry from 6 to 24 months, play audiometry from 2 to 5 years, or standard audiometry from 5 years).

• Recording of distortion product otoacoustic emissions in the frequency range up to 8–10 kHz.

• Tympanometry.

• Recording of short-latency and tone-specific auditory brainstem responses (e.g., auditory steady-state responses – ASSR) for infants when otoacoustic emissions are absent and pure-tone audiometry cannot be performed.

If hearing loss is detected, the patient is referred to an otolaryngologist-audiologist to determine an individual monitoring, treatment, and rehabilitation program. The audiological testing algorithm is presented in Appendix A3.1.

Comments: if congenital cardiovascular malformations are present, a geneticist and pediatric cardiologist consultation is required; if abnormalities are detected on Echo-CG and ECG, a pediatric cardiologist consultation is required. These diagnostic methods are indicated for all patients with a confirmed diagnosis of neuroblastoma prior to starting chemotherapy courses including cardiotoxic drugs (e.g., doxorubicin**) and subsequently upon completion of specific treatment and during long-term follow-up, considering the potential risk of delayed cardiotoxicity. If pathology is detected or clinical symptoms appear (dyspnea, edema), a pediatric cardiologist consultation is indicated.

Comments. Ultrasound can be used to assess the size and nature of skin and soft tissue metastases. Routine ultrasound is the primary imaging modality for all patients. It should include examination of the neck, abdominal cavity, especially the liver (small metastases may be missed if a high-frequency probe is not used), retroperitoneal space, and brain (if fontanelles are still open). Subsequently, ultrasound is performed before each course of chemotherapy and during follow-up.

Comments. In some cases, intrathoracic neuroblastoma can be detected on a chest X-ray in the presence of respiratory symptoms. Since chest ultrasound is limited due to air-filled lungs, monitoring of patients with intrathoracic neuroblastoma includes standard chest radiography rather than ultrasound. Chest radiography is also indicated after central venous catheterization to rule out pneumothorax and determine the catheter tip position.

Comments: to initially assess the extent of the tumor process, it is recommended to perform MSCT of the chest, abdomen, and pelvis.

MSCT of the neck and chest is performed in all patients to rule out secondary lung lesions, intrathoracic lymph node involvement, and multifocal disease in neuroblastoma.

MSCT is performed natively and with intravenous bolus phase contrast enhancement in the arterial, venous, and parenchymal phases of the study. The arterial phase of contrast enhancement corresponds to the first seconds of the scan, at the moment the contrast bolus enters the aorta. The venous phase of contrast enhancement occurs 60 to 80 seconds after contrast administration. The parenchymal phase of contrast enhancement occurs 1 minute 50 seconds to 2 minutes 30 seconds after contrast administration.

For specific considerations regarding tomographic imaging in children, see Section 7.2 of these guidelines.

Comments: Spinal cord MRI is strictly mandatory during initial staging in cases of paravertebral tumor location and/or in the presence of neurological symptoms suspicious for intraspinal tumor extension and spinal cord compression. If neuroblastoma is detected in the paravertebral region, MRI is required to document and confirm intraforaminal or intraspinal extension, even if the patient has no neurological manifestations. CT is not acceptable because small intraspinal tumor masses may be missed. In the presence of neurological symptoms (motor disturbances, sensory deficits, and pelvic organ dysfunction), contrast-enhanced MRI of the brain and spine is strictly mandatory.

MRI is preferred when the primary tumor is located in the neck and pelvis; it is strictly mandatory if there is evidence of metastatic liver involvement.

MRI can be used in infants for differential diagnosis between stage 4 and stage 4S neuroblastoma (to confirm or rule out bone, bone marrow, or subcutaneous metastases).

For all patients with stage 4 disease, despite the results of MIBG scintigraphy or other radioisotope imaging methods, a brain MRI must be performed to confirm or rule out intracranial and intraorbital involvement;

Brain MRI is indicated for initial staging in patients with primary MIBG-negative neuroblastoma or in patients who cannot undergo MIBG scintigraphy initially.

MRI is recommended in the presence of a single metastasis on MIBG scintigraphy or other radioisotope imaging methods to confirm its presence and topography.

MRI should not be replaced by MSCT for the following reasons:

• high spatial resolution;

• superior soft tissue contrast;

• better assessment of intraspinal and intraforaminal tumor extension;

• absence of ionizing radiation.

General anesthesia is mandatory for children under 6 years of age during the procedure.

Comments: Specific considerations for tomographic imaging in children.

1. To minimize artifacts from respiratory movements and potential involuntary reactions during contrast administration, young children require the procedure to be performed under anesthesia. Inhalation anesthesia is used for MSCT, and endotracheal anesthesia for MRI.

2. MSCT imaging in patients with suspected neurogenic tumors must be performed with intravenous bolus contrast enhancement.

3. Iodinated contrast agents are used in MSCT examinations. Prior to contrast administration, every patient, legal representative, or guardian must be informed about potential adverse reactions to the iodinated contrast agent and must sign an informed consent form for the procedure.

4. Access is established via a peripheral vein (catheter of variable diameter) or a central venous catheter (CVC, depending on its type). The injection rate of the contrast agent should be adapted to the patient's age and the diameter of the intravenous catheter.

5. The contrast dose is calculated individually based on the patient's weight. The dose is 1.5–2 mL/kg (max = 3 mL/kg); the injection rate ranges from 0.5 to 3.5 mL/s depending on the intravenous catheter diameter. The injection rate is most commonly in the range of 0.8 to 2.0 mL/s.

6. Whenever possible, MSCT scanning should be performed using dose-reduction software followed by reconstruction. For example, MSCT slice thickness of 5 mm followed by 0.625 mm reconstructions, gantry rotation time of 35 mm/rotation, table feed relative to gantry rotation of 1.75:1.

7. To reduce scanning time, it is recommended to use the minimum gantry rotation time by increasing the table speed. Tube voltage and current must be adapted to both the patient's age and weight and the anatomical region being scanned. Tube voltage is typically set between 100 and 120 kV, and tube current from 60 to 85 mA.

8. The radiological report for patients with neuroblastoma must include an indication of identified imaging risk factors in accordance with the recommended list.

9. When describing MSCT and MRI findings, the presence or absence of image-defined risk factors (IDRFs) must be reported to plan the timing and scope of surgical intervention.

10. All acquired MSCT and MRI images must be recorded and stored in the internationally recognized format for radiological studies—Digital Imaging and Communications in Medicine (DICOM).

MRI is performed in 3 planes: axial, coronal, and sagittal. All scans are performed using gadolinium-based contrast agents.

Paramagnetic bolus contrast enhancement in the arterial phase at the time of contrast administration, in the venous phase starting 50 seconds after contrast administration, and in the delayed phase 2–3 minutes after contrast administration.

Abdominal MRI is performed with respiratory gating of the scanning sequences, with a slice thickness of 3–4 mm

— T1-weighted native and T1-weighted post-contrast images in axial and coronal projections

— T2-weighted images in axial, coronal, and sagittal projections

— T2 FatSat/STIR (fat-suppression sequences) in axial and coronal projections

— Diffusion-weighted imaging (DWI) with ADC map generation.

MRI of the spine and paravertebral tissues for paravertebral neurogenic tumors is performed with a slice thickness of 3 mm.

— T1-weighted and T1-weighted FatSat/STIR images before and after contrast administration in axial, coronal, and sagittal projections

— T2-weighted and T2 FatSat/STIR (fat-suppression sequences) images in axial, coronal, and sagittal projections

—    Axial DWI of the region of interest

When performing CNS MRI, it is desirable to be able to simultaneously install head and spinal coils to examine the entire CNS without repositioning the patient.

When examining the brain:

—    Prior to contrast administration: T1-SE/TSE, T2-SE/TSE, T2FatSat/STIR, T2-FLAIR, DWI (with a b-factor of 1000 s/mm²) all in the axial projection. T1WI in the sagittal projection and T2FatSat/STIR in the coronal projection.

—    After contrast administration, T1-SE/TSE in all planes or T1 3D.

When examining the spinal cord:

—    Prior to contrast administration: T1-SE/TSE, T2-SE/TSE, T2-STIR in sagittal projections. Slice thickness 3 mm, interslice gap 0.5 mm.

—    After contrast administration: T1-SE/TSE sagittal (matching the native geometry), if necessary T1-SE/TSE axial of the region of interest.

• for establishing a diagnosis (when neuroblastoma is suspected);

• at initial staging of the tumor process;

• in assessing the efficacy of ongoing therapy;

• before and after surgical treatment;

• during follow-up monitoring after completion of therapy for early diagnosis of relapse;

• before planning other therapeutic options.

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Comments.

Patient preparation and precautions before ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy:

-          Discontinuation (cessation) of medications

This applies particularly to patients with tumors secreting catecholamine metabolites who may experience elevated blood pressure and consequently may take certain medications, such as α/β-blockers, that affect MIBG uptake. In children, the list of such medications is limited. However, the attending physician and radiologist must be informed in advance (prior to radiopharmaceutical administration) about the intake of certain agents. These medications include: bronchodilators containing fenoterol, salbutamol, terbutaline, nasal drops and sprays containing xylometazoline, α/β-blockers, calcium channel blockers, neuroleptics, and tricyclic antidepressants. For the duration of the procedure, it is necessary either to discontinue these medications or reschedule the procedure. The necessity of discontinuing certain medications or replacing them prior to MIBG scintigraphy should be evaluated by the attending physician.

-          Thyroid blockade

Thyroid blockade is performed using Lugol's solution or potassium iodide (tablets) to saturate the thyroid gland and prevent the accumulation of radioactive iodine.

A) Thyroid blockade using 1% #Iodine+[Potassium iodide+Glycerol] 1 drop per kg of the child's body weight per day, but not exceeding 40 drops per day; the daily dose should be divided into three intakes. Administration begins two days prior to MIBG injection and continues on the day of injection.

B) Thyroid blockade using #potassium iodide** (tablets): Newborns – 16 mg only on the day prior to radioactive iodine administration; 1 month – 3 years – 32 mg the day before radioactive iodine administration and then for 2 days (total 3 days); 3–13 years – 65 mg the day before radioactive iodine administration and then for 2 days (total 3 days); over 13 years – 130 mg the day before radioactive iodine administration and then for 2 days (total 3 days) [88,89].

 - To promote better excretion of the radiopharmaceutical, the patient is recommended to drink plenty of fluids.

- Foods containing vanillin and catecholamine-like substances (chocolate and blue cheese) must be excluded, as they can affect MIBG uptake.

Due to the duration of the study, pediatric patients require special preparation; experienced staff will talk with the parents and the patient, provide necessary assistance, and answer questions. Patients under 6 years of age generally undergo the procedure under anesthesia. Children undergoing the procedure without anesthesia may take water and food without time restrictions. Patients scheduled for the procedure under sedation/anesthesia must fast from all food and liquids for 6 hours prior to the procedure, with the exception of breastfeeding (in which case fasting is 4 hours).

Before MIBG injection

The radiologist must consider all clinical data of the patient and take into account any information that may assist in the interpretation of scintigraphic images:

—    history of suspected primary or residual tumor;

—    use of medications affecting MIBG biodistribution;

—    absence or presence of symptoms;

—    laboratory test results (levels of catecholamine metabolites, neuron-specific enolase, calcitonin, etc.);

—    results of other imaging modalities (MSCT, MRI, ultrasound, radiography);

—    prior treatment (surgery, chemotherapy, radiation therapy).

Calculation of ¹²³I-MIBG dose, administration, and timing of the study.

The minimum administered dose is 37 MBq, and the maximum dose should not exceed 370 MBq. To calculate the dose in children, the calculator on the European Association of Nuclear Medicine website www.eanm.org/publications/dosage-calculator can be used. On average, for children, ¹²³I-MIBG is administered at 4.2–5.2 MBq/kg, but not less than 37 MBq. The drug, reconstituted according to the manufacturer's instructions, is administered slowly intravenously, typically into a peripheral vein. If a central venous catheter (CVC) is present, especially in young children, the drug is administered through the CVC adhering to asepsis rules and infusion rate guidelines (slowly, over 5 minutes). Following ¹²³I-MIBG administration, the CVC is flushed with 10–20 ml of normal saline.

Side effects

Side effects (tachycardia, pallor, vomiting, abdominal pain) are related to the pharmacological effects of the molecule rather than allergy, and are very rare with correct, slow intravenous administration of MIBG.

Collimator selection

For ¹²³I-MIBG scintigraphy, both low-energy and medium-energy collimators can be used (3% of ¹²³I photons have energies above 400 keV, which may affect image sharpness and quality when using a low-energy collimator). Manufacturer recommendations, image quality, and clinical experience allow for the correct choice.

Study protocol (data acquisition)

The study is performed 24 hours after ¹²³I-MIBG administration. Standard imaging includes planar whole-body scanning in anterior and posterior projections, and lateral head projections (for better visualization of skull vault bones). Whole-body planar images are acquired at a table speed of 5 cm per minute on a 256x256 matrix. Target lateral head projections: data acquisition for 5–10 minutes. In cases of equivocal results and lack of technical equipment to perform the SPECT/CT protocol, delayed scanning is performed 48 hours post-injection. Scintigrams obtained 48 hours after MIBG administration show increased MIBG uptake in the tumor compared to physiological uptake. Furthermore, at 48 hours, washout and redistribution of physiological uptake occur (in the bowel, urinary tract, areas of atelectasis), which also facilitates differentiation from pathological uptake in masses. However, it should be noted that delayed studies exhibit increased image noise and, consequently, degraded image quality.

Currently, thanks to the availability of the SPECT/CT protocol, 48-hour studies are practically never performed. Performing the SPECT/CT protocol eliminates the need for another patient visit to the department for a repeat scan at 48 hours, as well as the need for additional anesthesia for children whose examinations can only be performed under sedation [20].

Performing SPECT and/or SPECT/CT protocols after acquiring whole-body planar images is in most cases not only very important but necessary, as it significantly improves the quality and diagnostic value of MIBG scintigraphy. SPECT data acquisition is performed under the following conditions: 3 degrees, 25–35 s, 128×128 matrix. The CT protocol is selected taking into account the child's body weight (kg).

Indications for SPECT and/or SPECT/CT protocols are quite broad and of great clinical significance for small tumors, large heterogeneous tumors that do not concentrate MIBG in the whole-body mode, when the tumor is located behind organs with physiological radiopharmaceutical uptake, for the differential diagnosis of soft tissue versus bone uptake, and for the differential diagnosis of physiological versus pathological uptake. SPECT/CT can be omitted only in cases of diffuse metastatic involvement.

Undoubtedly, performing the SPECT/CT protocol makes the procedure longer (an additional 30–40 minutes is required just for imaging one region of interest). However, the benefits gained from this imaging protocol significantly outweigh the disadvantage of increased scan time.

Normal MIBG Distribution

Normally, MIBG accumulates in the salivary glands, nasal mucosa, myocardium, liver, intestines, and urinary bladder. In some cases, MIBG uptake may be observed in the lacrimal glands, with small amounts accumulating in the spleen. Physiological increased MIBG uptake in brown adipose tissue is possible due to the sympathetic innervation of brown fat. Physiological MIBG uptake on planar images is visualized as symmetrically increased uptake, predominantly in the neck and supraclavicular regions. Inappropriate preparation leads to uptake in the thyroid gland. In patients after adrenalectomy, MIBG frequently accumulates in the remaining adrenal gland; the intensity of uptake may vary, which presumably reflects the degree of physiological functional compensation by the remaining adrenal tissue. As a rule, on planar scintigrams, MIBG uptake in the adrenal gland appears as focal accumulation in the paravertebral zone, most noticeable on the posterior detector. On fused SPECT/CT images, the uptake is localized above the renal region (at the expected site of the adrenal glands) and is associated with unchanged Y- or V-shaped adrenal glands. It is important to verify that focal MIBG uptake occurs precisely within the unaffected adrenal gland rather than in potentially adjacent soft-tissue or nodular pathological masses.

False-Positive Results

MIBG uptake mimicking pathology can occur in certain benign conditions such as atelectasis, pneumonia, focal nodular hyperplasia of the liver, radiation-induced liver injury, a large accessory spleen, focal pyelonephritis, and vascular malformations. Most of these false-positive results can be ruled out using SPECT/CT.

All questionable single lesions detected on ¹²³I-MIBG scintigraphy must be confirmed by other additional imaging methods. If there is no conclusive evidence of metastatic involvement, but the findings affect staging and risk group assignment, biopsies followed by histological examination must be performed.

• when ¹²³I-MIBG scintigraphy cannot be performed;

• in all ¹²³I-MIBG-negative neuroblastomas regardless of stage, to search for bone metastases when 18F-FDG PET/CT is not available;

• in case of questionable ¹²³I-MIBG scintigraphy results for the differential diagnosis between bone marrow involvement and bone tissue involvement;

• if initial ¹²³I-MIBG scintigraphy was not performed, and an examination carried out after the initiation of specialized treatment showed no pathological uptake foci;

• in the absence of pathological uptake foci during ¹²³I-MIBG scintigraphy performed after surgical treatment, when 18F-FDG PET/CT is not available.

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Comments. The sensitivity and specificity of this method are relatively low. The procedure is performed based on clinical indications and only when MIBG scintigraphy or 18F-FDG PET/CT is unavailable.

No special preparation is required for the study. For children scheduled for the procedure under anesthesia, all food and liquids must be withheld for 6 hours prior to the scan, with the exception of breastfeeding (in which case the fasting period is 4 hours).

The procedure is performed 2.5–3 hours after intravenous administration of the radiopharmaceutical via a central or peripheral catheter at a dose of ≈7 MBq/kg. To calculate the dose, the EANM dosage calculator available at www.eanm.org/publications/dosage-calculator can be used.

No significant side effects from the administration of the radiopharmaceutical have been reported.

Data acquisition parameters for whole-body planar imaging: detectors in the "anterior and posterior" position with low-energy high-resolution collimators; isotope energy peak of 140 keV; energy window width of 10%; table speed of 8 cm/min. Static lateral views of the head are acquired by collecting gamma quanta for 5 min into a 256x256 matrix. The SPECT protocol is performed only upon the instruction of the radiologist after reviewing the planar images: detector rotation angle of 6⁰ degrees, acquisition time of 20 seconds, on a 128x128 matrix. To obtain fused SPECT/CT images, low-dose CT is performed (for anatomical localization and attenuation correction) taking into account the patient's body weight (kg).

Physiological hyperfixation of the radiopharmaceutical in skeletal growth zones prevents reliable detection of metastatic involvement in these areas.

All questionable single lesions detected on bone scintigraphy with ^99mTc-phosphate complexes must be confirmed by other additional imaging methods. If there is no conclusive evidence of metastatic involvement, but the findings affect staging and risk group assignment, biopsies followed by histological examination must be performed.

- evaluation of disease extent in patients with primary MIBG-negative neuroblastoma;

- in the presence of questionable/contradictory results from 123I-MIBG scintigraphy and CT/MRI findings;

- evaluation of disease extent in 123I-MIBG-negative patients evaluated after primary tumor resection.

LoE AGoE 2Level of Evidence A (Grade of Recommendation 2)

Comments: The procedure is performed strictly on an empty stomach (no food intake for at least 6 hours prior to the scheduled time). Patients undergoing the procedure without anesthesia are allowed to drink plain drinking water (non-sweet and non-carbonated). For patients scheduled for the procedure under anesthesia, food and liquids must be withheld for 6 hours prior to the scan.

Come to the appointment wearing warm, comfortable clothing without zippers, metal rivets, buttons, etc.

Exclude physical exertion and the consumption of easily digestible (fast) carbohydrates 24 hours prior to the study.

The radiopharmaceutical (¹⁸F-FDG) is administered intravenously via a central or peripheral catheter at a dose of 5.2 MBq/kg. The minimum administered dose must be at least 75 MBq, and the maximum no more than 400 MBq. To calculate the dose in children, the calculator on the European Association of Nuclear Medicine website (www.eanm.org/publications/dosage-calculator/) can be used. The administered dose may be reduced while maintaining the scan time when performing the study on modern equipment (see the manufacturer's recommendations and the recommendations on the website www.eanm.org/publications/dosage-calculator/). The study is performed approximately 60 minutes after the IV administration of the radiopharmaceutical in whole-body mode with a data acquisition speed of 3 min/bed position (depending on the PET/CT scanner characteristics and the administered dose, the data acquisition speed may be either decreased or increased). The CT protocol is selected taking into account the child's body weight (kg).

No significant adverse effects of the radiopharmaceutical administration have been reported.

To minimize the number of false-positive and false-negative results, the initial study must be performed before the patient starts treatment. The referral for the scan must be accompanied by a detailed medical summary including dates and protocols of surgeries, various instrumental examinations (imaging reports and external storage media – discs), and indicating diagnosed foci of infection (if any).

All doubtful single lesions detected by FDG PET/CT must be confirmed by other additional imaging modalities. In the absence of conclusive evidence of metastatic involvement, yet affecting the determination of stage and risk group, a biopsy followed by histological examination must be performed.

Comments: thus, ¹⁸F-DOPA is a direct precursor of dopamine and its accumulation mechanism is similar to catecholamine metabolism; therefore, ¹⁸F-DOPA PET can be a good alternative to ¹²³I-MIBG scintigraphy for patients with neuroblastoma.

High expression of somatostatin receptors on neuroendocrine tumor cells, including neuroblastoma cells, makes it possible to use nuclear medicine methods utilizing ⁶⁸Ga conjugated with a somatostatin analogue molecule (DOTA-TOC, DOTA-NOC, DOTA-TATE) [24, 25].

Another radiopharmaceutical for PET/CT in children with neuroblastoma that currently demonstrates good diagnostic efficacy and is being widely studied is metofluorobenzylguanidine labeled with ¹⁸F (¹⁸F-mFBG) [26]

The radiopharmaceuticals for PET/CT indicated above can be used as an alternative to ¹²³I-MIBG scintigraphy in children with neuroblastoma during initial evaluation (primary staging), for assessing treatment response, and for detecting disease relapse.

2.5 Other Procedures

Comments: bone marrow involvement in neuroblastoma is focal. Therefore, bone marrow puncture from a single site is not acceptable. Bone marrow punctures from at least 4 different sites are required. Additionally, children older than 12 months must undergo trephine biopsy from 2 sites. When performing a bone marrow puncture, it is advisable to prepare 10 slides from each site. Thus, when performing a bone marrow puncture from 4 sites, the total number of slides will be 40. Trephine biopsy is not performed in infants under one year of age.

Additionally, bone marrow involvement assessment using myelogram and trephine biopsy is performed at treatment stages and during follow-up if disease progression is suspected.

Comments: after a comprehensive examination within the framework of the previously described algorithm, all patients are considered candidates for initial surgical intervention, the extent of which is determined after joint discussion by a pediatric oncologist, pediatric surgeon, ultrasound diagnostics physician, and radiologist. During preoperative planning, the topography of the primary tumor and its relationship with vital structures (main vessels, parenchymal organs, etc.) are assessed, and surgical risk factors based on visualization data—IDRF—are determined.

The method of choice for surgical access to perform a tumor biopsy is "open" access (laparotomy, thoracotomy) and minimally invasive access (laparoscopy, laparotomy). These methods allow obtaining a sufficient amount of tissue for histological and cytogenetic examinations [27, 28].

Patients with a localized tumor up to 7 cm in the retroperitoneal region and up to 9 cm in the posterior mediastinum in the absence of surgical risk factors, namely in the absence of total involvement of a major artery by the tumor and with preservation of the major vein lumen, may be candidates for minimally invasive surgical treatment. Complete resection is indicated only if the anticipated risk of postoperative complications is low. The surgery should not be mutilating (e.g., nephrectomy). If the anticipated risk of complications is high, partial tumor resection or biopsy alone is permissible. See also Section 7.4.

Metastasis biopsy.

In a number of cases, biopsy of metastatic lesions is possible. For example, biopsy of subcutaneous metastases, liver biopsy in stage 4S NB, biopsy of distant metastatic lymph nodes, etc.

Pathomorphological examination is the main method for final verification of the diagnosis in patients with neuroblastoma. The report must indicate the neurogenic tumor variant according to the International Neuroblastoma Pathology Classification [29].

Tumor histology and molecular genetic testing are critical for risk stratification of patients with localized forms of neuroblastoma, stage 4S, and stage 4 in infants under one year of age. Therefore, tumor biopsy is always required in localized forms of the disease.

In stage 4 disease, MYCN status and 1p chromosome status can be evaluated in the bone marrow provided that tumor cell infiltration exceeds 60%. Determination of other parameters (e.g., tumor-associated antigens) is not possible using bone marrow samples. Therefore, open biopsy to obtain tumor tissue is recommended even for patients with stage 4 disease.

The pediatric oncologist must oversee the collection of tumor material. Close cooperation between the pediatric oncologist and the pathologist is a prerequisite for obtaining and submitting an adequate volume of tumor tissue. Processing and sectioning of the tumor tissue must be performed by a pathologist in the regional laboratory. The tumor tissue must be delivered from the operating room to the pathology laboratory immediately and processed within 30 minutes. If tissue cryopreservation is feasible (availability of liquid nitrogen for snap freezing and a low-temperature storage facility maintaining a temperature of –80 °C or lower), the pathologist may divide the sample into a fragment(s) required for diagnosis and a tissue fragment for cryopreservation for subsequent molecular genetic testing. The pathologist determines which part of the tumor can be frozen without compromising the diagnosis. If possible, they should collect material from at least 2 macroscopically distinct areas (if present). Tissue designated for cryopreservation must be divided into fragments not exceeding 50 mg in mass or 3×3×3 mm in linear dimensions. One tissue fragment is placed in a cryovial (a 1.5–2 ml vial with a screw cap and rubber O-ring), which must be labeled (indicating the patient's personal data, date and time of cryopreservation, and the stage of biomaterial collection [initial diagnosis, second-look surgery, biopsy for relapse verification]) and immediately immersed in liquid nitrogen (volume of 200–500 ml). After complete evaporation of the liquid nitrogen, the vial is transferred to a freezer (temperature not exceeding –80 °C). Cryopreservation of tissue in a household refrigerator freezer is strictly prohibited!

Tumor imprints must be made before placing the material in formalin. In addition, peripheral blood should be collected for molecular analysis.

The tissue remaining after cryopreservation, or all tumor tissue if cryopreservation is not feasible, is fixed in buffered 4% formalin for histological examination. Multiple blocks from macroscopically distinct areas of the tumor, especially tumor nodules, should be collected. Areas of necrosis and regressing tumor tissue should be collected in proportion to their volume relative to the entire tumor volume, which will allow for accurate determination of the degree of regression.

The pathologist in the local pathology laboratory must classify the tumor in accordance with the International Neuroblastoma Pathology Classification, including the assessment of the mitosis-karyorrhexis index. The degree of regression, differentiation, and resection margin involvement must also be evaluated. Depending on the degree of differentiation, the mitosis-karyorrhexis index, and the patient's age, tumors are categorized into favorable and unfavorable types.

Following chemotherapy, the tumor must be classified in accordance with the aforementioned scheme, with indication in the histological examination report,

Comments: evaluation of molecular genetic markers is a mandatory diagnostic test in patients with neuroblastoma.

For therapeutic stratification, the status of the MYCN oncogene and the distal part of chromosome 1p (1p36) should be evaluated using the following techniques: fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR).

Criteria for MYCN and 1p status by FISH

MYCN gene amplification is defined as a 4-fold or greater increase in the number of MYCN gene copies compared to the number of chromosome 2 (the control region used to determine chromosome number 2 is the chromosome 2 centromere).

The concept of "MYCN gain" (presence of additional copies) is defined as a ratio of MYCN gene copies to the chromosome 2 control region ranging from 1.5 to 4.

Deletion of the 1p region is defined as the presence of a single signal from the corresponding 1p36 region in 33% or more of the nuclei examined. Imbalance of the 1p region was defined by the predominance of signals from the 1(q25) control region over the number of signals from the 1(p36) region.

Criteria for MYCN and 1p status by PCR

To assess MYCN status, real-time quantitative PCR is performed with the detection of MYCN gene fragments and a reference gene (e.g., POLR2D or NAGK). The number of MYCN gene copies is calculated using the formula:

N=2^{- (Cq MYCN - Cq RG)} ×2,

Where N is the number of MYCN gene copies, CqMYCN is the PCR threshold cycle value for the MYCN gene, and CqRG is the PCR threshold cycle value for the reference gene. A value of ≤2 indicates a normal copy number (equal to 2); 3–9 indicates an increase in copy number below the amplification threshold (gain), which may be observed with tri- and tetraploid chromosome sets (FISH analysis is required for clarification); ≥10 indicates MYCN gene amplification.

Determination of 1p status is performed by standard PCR with detection of microsatellite repeats in the short arm of chromosome 1 (D1S2697, D1S436, D1S214, D1S2663, D1S80, D1S76). Parallel analysis of tumor tissue and constitutional material (DNA from peripheral blood leukocytes or buccal epithelial cells) is required. If two PCR products are detected for each locus in both the tumor and constitutional material, a heterozygous (normal) state of the short arm of chromosome 1 is determined. If a single PCR product is detected, it is a homozygous state, and the analysis for this locus is uninformative. If a single PCR product is detected in the tumor tissue DNA analysis and two products in the constitutional DNA analysis, this indicates loss of heterozygosity associated with 1p deletion.

Most frequently, the deletion affects distally located loci: D1S436, D1S80, D1S76).

Multiplex Ligation-dependent Probe Amplification (MLPA) method

Determination of the MYCN copy number, the short arm of chromosome 1, and other clinically significant chromosomal regions and genes (ALK, 11q) can be performed using Multiplex Ligation-dependent Probe Amplification (MLPA) with SALSA MLPA reagent kits P251, P252, P253. Data analysis is carried out using Coffalyser.NET software. A normalized signal ratio from the corresponding locus of <0.75 is interpreted as a deletion, 0.75–1.25 as a normal copy number, 1.25–3.00 as an increased copy number, and >3.00 as amplification.

For high-risk patients, as well as in cases of relapse, progression, and refractory disease, it is advisable to perform molecular genetic testing to identify targets for molecularly targeted therapy. These primarily include activating missense mutations in the tyrosine kinase domain of ALK (p.F1174L, p.F1245V/C, p.R1275Q), which can be detected by allele-specific PCR or Sanger sequencing. The absence of mutations in "hot spots" does not rule out the presence of other activating variants in the ALK gene or rare potentially targetable aberrations (mutations in BRAF, PDGFRA, and other genes). Therefore, when technically feasible, high-throughput DNA sequencing of DNA isolated from tumor tissue is recommended. A rare predictive marker of potential efficacy for ALK inhibitors is amplification of the corresponding gene, which can be detected using FISH or MLPA [30].

- pediatric oncologist (hematologist);

- neonatologist (for infants in the first months of life);

- neurologist;

- ophthalmologist;

- pediatric surgeon;

- medical geneticist;

- neurosurgeon (in the presence of neurological symptoms);

- anesthesiologist-resuscitologist and other specialist physicians.

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

Management of patients with NB is carried out depending on the disease stage and risk group [13]. These guidelines are developed on the basis of the NB-2004 protocol [13].

Before initiating any type of therapy, the physician obtains informed voluntary consent from the patient over 15 years of age (or from the parents/legal representatives of the patient for patients under 15 years of age) in written form.

The patient (parents/legal representatives) should be provided with an explanation including: accessible information regarding the diagnosis, the scope of upcoming treatment, the necessity of chemotherapy, prognosis without appropriate therapy, prognosis with adequate therapy, the possibility of developing refractory disease, the main mechanisms of action of chemotherapy drugs (including early and delayed side effects), the need to follow patient care regimens, basic dietary rules, the necessity of central venous catheterization, the need for blood product transfusions, and the risk of potential transfusion complications.

Comments: it should be noted that a number of studies have revealed an increased risk of infectious complications in patients with a central venous catheter; therefore, monitoring, timely prevention, and control of potential catheter-associated complications are required [33-35].

• Stage 1, age 0–18 years, absence of MYCN gene amplification

• Stage 2, age 0–18 years, absence of MYCN gene amplification, absence of 1p aberrations (del1p, imb1p)

• Stage 3, age 0–2 years, absence of MYCN gene amplification, absence of 1p aberrations (del1p, imb1p)

• Stage 4S, age <1 year, absence of MYCN gene amplification

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

Comments: evaluation of molecular genetic markers is a mandatory diagnostic test in patients

• Stage 2/3, age 0–18 years, absence of MYCN gene amplification, presence of 1p aberrations (del1p, imb1p)

• Stage 3, age 2–18 years, absence of MYCN gene amplification

• Stage 4, age <1 year, absence of MYCN gene amplification

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

• Stage 4, age 1–18 years

• MYCN gene amplification regardless of disease stage and age

Level of Recommendations CLevel of Evidence 5Level of Recommendations C (Level of Evidence 5)

Comments: patients with stage 1 according to the INSS staging system and stage L1 according to the INRGSS staging system in the presence of MYCN gene amplification may be stratified into the intermediate-risk group (avoiding high-dose chemotherapy, auto-HSCT, and GD2 immunotherapy) provided that the full complex of diagnostic examinations is performed (including mandatory 123I-MIBG scintigraphy or other radioisotope imaging methods (see above) prior to surgical intervention. The management strategy for these patients must be coordinated with a national/federal specialized center [36].

It is mandatory to have a detailed surgical report confirming macroscopically complete tumor resection and post-operative imaging (MSCT/MRI) demonstrating the absence of residual tumor.

Patients with stage 4 disease according to the INSS staging system or stage M according to the INRGSS staging system aged 12 to 18 months in the absence of MYCN gene amplification and other segmental abnormalities confirmed by MLPA may be stratified into the intermediate-risk group (avoiding high-dose chemotherapy, auto-HSCT, and GD2 immunotherapy). The management strategy for these patients must be coordinated with a national/federal specialized center [37].

1. Treatment of patients in the observation group (low risk)

The initial therapeutic volume for patients stratified into the observation group is determined based on the extent of the tumor process (localized forms of the disease or stage 4S) and the presence of life-threatening symptoms (LTS) at the time of diagnosis.

Comments: during preoperative planning, the topography of the primary tumor and its relationship with vital structures (major vessels, parenchymal organs, etc.) are evaluated—image-defined risk factors (IDRF). Complete resection is indicated only if the estimated risk of postoperative complications is low (typically patients without IDRF). The surgery should not be mutilating (e.g., nephrectomy). If the estimated risk of complications due to the presence of IDRF is high, partial tumor resection or biopsy alone is acceptable.

Comments: in the group of patients with stages 1–3 of the disease without initial vital structure involvement, adjuvant chemotherapy is not indicated, regardless of the extent of surgery performed and the size of the residual tumor. All patients in this group undergo active surveillance (the schedule is presented in the relevant section). The scope and timing of examinations differ between patients with stages 1–2 without macroscopic tumor and patients with stages 2–3 in the presence of a macroscopically residual tumor. If a residual tumor is present, regular follow-up is carried out up to 2 years of age (if age at diagnosis is less than 1 year) or 12 months after the initial surgery (if age at diagnosis is 1 year or older). Upon confirmation of complete tumor regression, dispensary follow-up continues within the framework of recommendations for patients who have achieved a complete response. If the residual tumor persists, the possibility of surgical intervention for its removal is discussed.

Comments: in the case of LTS at initial diagnosis, detection of local progression of the residual tumor, and/or the appearance of LTS during active surveillance, chemotherapy according to the N4 regimen is indicated, including vincristine**, doxorubicin**, and cyclophosphamide** (see Appendix A3.2).

Criteria for initiating a chemotherapy cycle:

● leukocytes > 2000/µL;

● lymphocytes > 1000/µL;

● platelets > 50,000/µL;

● absence of signs of infection.

Response to therapy is assessed after each treatment cycle (response assessment includes imaging studies—MSCT and MRI). Chemotherapy is completed as soon as resolution of LTS and stabilization of the tumor process are noted. If LTS persist or the tumor process progresses further, chemotherapy according to the N4 regimen is continued. The maximum number of therapy cycles is 4. If tumor control is not achieved after 4 cycles of the N4 regimen, the patient is transferred to a more intensive therapy program originally developed for intermediate-risk patients (cycles N5, N6 – see Appendix A3.2). It must be emphasized that prior to transferring the patient to more intensive therapy, it is recommended to perform a repeat biopsy or tumor removal with re-evaluation of molecular genetic markers, as well as the degree of drug pathomorphosis and tumor cell differentiation.

LTS include the following conditions caused by local growth of the primary tumor (in stages 1–3) or organomegaly due to metastatic involvement (e.g., metastatic liver involvement in stage 4S):

● severe general condition;

● severe nutritional disorders leading to a reduction in single feeding volume and/or weight loss;

●    respiratory failure, defined by the need for oxygen supplementation (or mechanical ventilation) to maintain arterial blood $pO_2$ above 60 mm Hg, pulse oximetry oxygen saturation above 90%, or $CO₂$ elimination exceeding 60 mm Hg;

●    cardiovascular failure, defined as arterial hypotension or hypertension; tachycardia/bradycardia according to age-related normal blood pressure and heart rate values;

●    hepatic failure, defined as grade III toxicity for bilirubin, fibrinogen, or thrombin time according to the National Cancer Institute Common Toxicity Criteria;

●    renal failure, defined by impaired urea or creatinine excretion, newly developed hydroureter or hydronephrosis, or worsening of pre-existing hydronephrosis;

●    intraspinal tumor extension with the development of epidural compression symptoms, or intraspinal extension documented by MRI regardless of the presence of symptoms, depending on the level of invasion into the spinal canal and the degree of spinal cord compression;

●    failure of other organs or systems.

Following a comprehensive workup within the framework of the previously described algorithm, all patients are considered candidates for initial surgical intervention, the extent of which is determined after a joint discussion by pediatric oncologists, surgeons, ultrasound diagnostics specialists, and radiologists.

Following initial surgical intervention and histological examination of the surgical specimen, the disease stage is definitively verified according to the INSS system, and the presence of life-threatening symptoms (LTS) is reassessed.

In the group of patients with stage 1–3 disease presenting with initial LTS, the indications for adjuvant chemotherapy after initial surgical intervention are evaluated depending on the surgical efficacy in controlling LTS. If LTS have been resolved by surgery, chemotherapy is not indicated. If LTS persist, adjuvant chemotherapy according to the N4 regimen is administered, with response and LTS severity assessed after each cycle. Therapy is completed as soon as LTS resolution is documented. 

1.1. Management of observation group (low-risk) patients who develop abdominal compartment syndrome

Comments. If neuroblastoma is complicated by a significant increase in intra-abdominal pressure, a specific condition known as abdominal compartment syndrome (ACS) develops. This condition is characterized by tissue destruction due to compression ischemia and microcirculatory disorders, accompanied by the development of multiple organ dysfunction syndrome (MODS). As a rule, ACS is accompanied by the development of LTS, for which admission to the intensive care unit is indicated.

Indications for transferring patients to the ICU include:

1. secondary respiratory failure (need for high-flow oxygen therapy, decrease in saturation to 90% and below; dyspnea, tachypnea, high work of breathing, hypercapnia/hypoxemia according to blood gas analysis).

2. cardiovascular failure (arterial hypotension/hypertension, tachycardia/bradycardia, cardiac arrhythmias).

3. acute renal failure (decrease in urine output rate below 1 mL/kg/h, no response to fluid therapy and loop diuretics, high azotemia levels, clinical signs or high risk of tumor lysis syndrome).

4. development of infectious complications (sepsis, septic shock).

5. neurological disorders (impaired level of consciousness, seizure syndrome).

6. severe water-electrolyte disturbances unresponsive to correction at previous stages of care, requiring careful and frequent laboratory monitoring.

Intra-abdominal pressure (IAP)

Intra-abdominal pressure (IAP) is defined as the steady-state pressure within the abdominal cavity. The normal IAP level ranges from 5 to 7 mm Hg and does not significantly depend on sex, body weight, or even artificial ventilation.

The level of intra-abdominal pressure directly depends on the volume of hollow organs, the presence of ascites, blood, and other space-occupying lesions/masses (including, for example, retroperitoneal neuroblastoma).

Methods for measuring IAP are divided into direct (during laparoscopy) and indirect. Currently, the "gold standard" for indirect measurement is the use of the urinary bladder. The elastic and highly distensible wall of the urinary bladder acts as a passive membrane and accurately transmits intra-abdominal pressure.

A contraindication to this method is bladder injury or its compression by a hematoma or tumor. If contraindications are present, intragastric pressure measurement can be used as an alternative.

Method of intravesical pressure measurement: under aseptic conditions, a urological (urinary) catheter is inserted and the bladder is emptied. With the patient in a horizontal supine position, warm sterile normal saline is injected into the urinary catheter at a dose of 1 ml/kg of body weight, not exceeding 25 ml.

Measurements are taken over 2 minutes. The mid-axillary line is used as the zero reference point.

Values are converted to mmHg based on the ratio 1 mmHg = 1.36 cm H2O (the measurement result should be divided by 1.36).

Important notes: if the patient is on mechanical ventilation, it should be taken into account that the PEEP level increases intra-abdominal pressure (IAP). For a more accurate result, the positive end-expiratory pressure level should be subtracted (based on 1 mBar = 1 cm H2O).

Intra-abdominal hypertension (IAH) is a persistently or intermittently (but not transiently) recorded pathological increase in IAP above 12 mmHg. There are several grades of IAH according to the criteria of the World Society of the Abdominal Compartment Syndrome (WSACS) (adapted by B.R. Gelfand, 2008) [61]:

●            Grade I – 12–15 mmHg

●            Grade II – 16–20 mmHg

●            Grade III – 21–25 mmHg

●            Grade IV – >25 mmHg

In children, WSACS norms with pediatric adjustments are applied:

●            Grade I – 10–12 mmHg

●            Grade II – 13–15 mmHg

●            Grade III – 16–18 mmHg

●            Grade IV – >18 mmHg

Abdominal compartment syndrome (ACS) is a sustained increase in intra-abdominal pressure above 20 mmHg accompanied by the development of organ failure or organ/organ system dysfunction. The rate of intra-abdominal volume increase plays a significant role. The severity of the clinical course and the likelihood of multiple organ dysfunction syndrome (MODS) increase in proportion to the rate of IAH progression, because with a rapid volume increase, the compensatory stretch capacity of the anterior abdominal wall does not have time to develop.

At the tissue level, ACS manifests as decreased oxygen delivery, hypoxia, ischemia, and a shift to anaerobic metabolism with the release of endothelium-damaging bioactive substances, nonspecific inflammatory mediators, and vasoactive substances (interleukins, serotonin, histamine, etc.), leading to increased endothelial permeability and interstitial edema, which exacerbates ischemia and impairs transmembrane transport. Ultimately, this results in the development of MODS.

The following clinical symptoms play a role in the diagnosis of ACS:

• presence of pain syndrome;

• abdominal distension and tension;

• dyspnea, signs of respiratory failure progressing despite mechanical ventilation;

• decreased urine output;

• decreased cardiac output, cardiac volumes, and indices;

• impaired gastrointestinal transit.

Assessment of respiratory function, indications for mechanical ventilation.

In abdominal compartment syndrome (ACS), high diaphragmatic elevation causes an increase in intrathoracic pressure (from 25% to 80% of the total intra-abdominal pressure level). This leads to a decrease in functional residual capacity of the lungs, dynamic pulmonary compliance, an increase in dead space and blood shunting, collapse of basal alveoli, and the development of areas of atelectasis. Respiratory failure develops (increase in PaCO2, decrease in PaO2, development of respiratory acidosis).

To objectively assess lung tissue damage and for the differential diagnosis of respiratory failure, it is advisable to perform a chest X-ray and computed tomography, as well as an ultrasound examination of the pleural cavities.

Indications for transferring the patient to mechanical ventilation may include the following clinical symptoms:

- absence of breathing (apnea) or abnormal breathing patterns;

- high work of breathing;

- Hypercapnia (PaCO2) >55–60 mmHg; and/or hypoxemia (PaO2) <55–50 mmHg;

- Compensated/Decompensated respiratory alkalosis (PaCO2 <25 mmHg)

- Decrease in pvO2 <30 mmHg

- Decrease in SvO2 less than 60% (Oxygen extraction ratio >40%)

- inefficient oxygenation (decrease in saturation <90% despite oxygen supplementation);

- development of parenchymal respiratory failure (radiological picture of ARDS);

- Decrease in the blood respiratory index (PaO2/FiO2) <200 or (SpO2/FiO2) <200;

- Hemodynamic disturbances (life-threatening rhythm disorders, hypotension, etc.);

- Refractory septic shock with a high requirement for sympathomimetic therapy.

During mechanical ventilation, it is recommended to avoid exceeding Pinsp >35–38 mmHg due to the risk of barotrauma. At high Pinsp values (greater than 30 mBar), the use of myoplegia with non-depolarizing muscle relaxants (rocuronium at a dose of 0.4–0.6 mg/kg/h) is advisable.

In some cases, it is preferable to ventilate the patient in Volume Control modes, determining the tidal volume at 5–7 ml/kg in order to reduce the mean airway pressure (Pmean).

30–60 minutes after the initiation of mechanical ventilation, it is recommended to perform a blood gas and acid-base balance (ABB) analysis to adjust mechanical ventilation parameters. Subsequently, ABB is monitored every 6 hours.

Assessment of the cardiovascular system, cardiotonic support.

Mechanical compression of the inferior vena cava and portal veins, along with activation of the renin-angiotensin-aldosterone system, leads to a decrease in venous return and an increase in total peripheral vascular resistance.

Simultaneously, an increase in intrathoracic pressure occurs, leading to compression of the heart and great vessels, and a decrease in end-diastolic volume.

Hypovolemia, present in the majority of cases, and the use of high PEEP levels during mechanical ventilation can further exacerbate the manifestations of cardiovascular failure.

Clinically, signs of cardiovascular failure may include:

- arterial hypotension unresponsive to fluid challenge;

- arterial hypertension;

- changes in heart rate (tachycardia, bradycardia);

- life-threatening cardiac arrhythmias.

Table 7.3.1. Normal values of Mean Arterial Pressure (MAP), mmHg:

To assess the dynamic parameters of the cardiovascular system, it is recommended to measure cardiac output, cardiac volumes, and indices:

● Normal CI: 3.5–5.5 L/(min · m²)

● stroke index: 30–60 mL/m²

● SVRI (systemic vascular resistance index): 800–1600 dyn · s · cm⁻⁵/m²

In the presence of signs of hypovolemia, fluid administration at 20 mL/kg is advisable.

It should be noted that measuring central venous pressure (CVP) is not a reliable diagnostic criterion, since intra-abdominal hypertension causes compression of the central veins. A reliable instrumental method for determining hypovolemia in intra-abdominal hypertension is the measurement of left ventricular end-diastolic volume (echocardiography).

If bolus fluid challenge is ineffective, hypotension persists, and signs of tissue hypoperfusion are present (mottling of the skin, increasing blood lactate levels), the patient is indicated for sympathomimetic therapy. Determining the cardiac index (CI) may be helpful when choosing the drug.

• Cardiac index 3.5–4 L/min/m² – dopamine** (5–20 mcg/kg/min) or norepinephrine (0.1–0.3 mcg/kg/min, preferably not exceeding 1 mcg/kg/min),

• Cardiac index <3.5 L/min/m² – dobutamine** (5–20 mcg/kg/min, possibly in combination with norepinephrine** or dopamine**).

One of the most accurate predictors of visceral perfusion is the abdominal perfusion pressure (APP) level, which is determined by the levels of systolic and intra-abdominal pressure: APP = MAP – IAP.

It has been proven that APP <60 mmHg directly correlates with the survival of patients with intra-abdominal hypertension. The main goal of cardiotonic support in intra-abdominal hypertension is to maintain an abdominal perfusion pressure level >60 mmHg.

Assessment of renal failure, indications for renal replacement therapy.

In ACS, both arterial and venous renal blood flow suffer. This is due to direct compression of the renal vessels (renal veins are more susceptible to compression) as well as the release of vasoactive mediators, such as endothelin and/or hormones of the renin-angiotensin-aldosterone system. A decrease in venous return leads to a decrease in the secretion of atrial natriuretic peptide. The above factors lead to a decrease in the glomerular filtration rate.

Daily urine output decreases by more than half at IAP values up to 15 mmHg (persisting for 24 hours). An increase in IAP to 20–30 mmHg leads to anuria unresponsive to diuretic therapy.

When urine output drops below 0.5 mL/kg/h and edema syndrome develops, the patient is indicated for therapy with loop diuretics (furosemide**) at a dose of 5–10 mg/kg/day.

If acute kidney injury is suspected, careful monitoring of potassium levels (2–4 times a day), azotemia (creatinine, urea, cystatin C; at least 2 times/day), and fluid balance control is necessary, preferably with regular weighing of the patient.

Table 7.3.2 Normal creatinine levels depending on age, mg/dL:

Main indications for initiating renal replacement therapy include:

- Fluid overload with clinically significant organ and tissue edema (especially pulmonary edema) or positive fluid balance >20–40 mL/kg/24 h;

- Non-obstructive oliguria/anuria (decrease in urine output rate below 0.5 mL/kg/h) resistant to diuretic therapy (Lasix 10 mg/kg/day) for 6–12 hours;

- Hyperkalemia (K+ >6–6.5 mmol/L) or rapid progression of hyperkalemia;

- Severe dysnatremia (115 < Na < 160 mmol/L);

- Azotemia (creatinine 250–300 µmol/L, or an increase of 40–44 µmol/L/day or more; urea >25–30 mmol/L).

Assessment of the central nervous system and level of consciousness.

Against the background of increased intrathoracic pressure, patients experience impaired blood outflow through the jugular veins, which can manifest as intracranial hypertension.

When the level of consciousness on the Glasgow Coma Scale drops to stupor or lower, the patient is indicated for mechanical ventilation.

Assessment of liver failure and hemostatic function.

If the synthetic function of the liver decreases, the patient is indicated for correction:

- if the albumin level drops <20 g/L, emergency correction is indicated (preferably with 20% albumin to reduce the risk of volume overload) at a rate of 1 g/kg over 1 hour. If the albumin level is 20-29 g/L, correction by continuous infusion is indicated at a rate of 1-2-2.5 g/kg/day.

- if the fibrinogen level drops below 1 g/L, or in the presence of signs or a high risk of hemorrhagic syndrome, FFP replacement therapy (15-20 ml/kg) or cryoprecipitate (1 dose (40 ml) per 10 kg) is indicated.

- in the presence of hemorrhagic syndrome, it is advisable to maintain the platelet count at least 50 × 10^9/L. Replacement therapy is performed with platelet concentrate (at a rate of 1 dose per 10 kg).

Evaluation of gastrointestinal function.

Gastric tube placement is indicated for patients for gastric decompression.

Clinical studies have demonstrated a correlation between ACS and the development of hypoperfusion and ischemia in the intestinal mucosal wall, with translocation of intestinal flora and toxins into the portal circulation and lymph nodes. Therefore, there is a high risk and high incidence of infectious complications of various localizations, making anti-infective therapy appropriate (broad-spectrum antibiotics, antifungal therapy).

To identify potential causative agents of the infectious process and to de-escalate anti-infective therapy, thorough microbiological monitoring is required, including cultures of bronchoalveolar lavage fluid (1-2 times a week), blood cultures (1-2 times a week, additionally according to clinical indications), cultures of ascitic/pleural fluid, gastric and intestinal contents, and other body secretions. To rule out the involvement of viral flora, PCR assays are advisable (primarily BAL, blood), addressing the issue of whether antiviral therapy is indicated.

1.2. Management of patients under observation (low risk) upon the development of epidural compression.

Comments. In 10-15% of cases, hourglass-shaped NBs extend into the intervertebral foramina and/or spinal canal at one or multiple levels. Relative to the spinal cord, the tumor mass is always located epidurally. In 5-7% of patients, symptoms of spinal cord compression of varying severity (epidural compression - EC) are detected – back pain, paraparesis or paraplegia, pelvic organ dysfunction, and sensory disturbances. In some cases, these are the patient's initial complaints. Symptoms may arise acutely, but more often develop gradually over many weeks and even months. Sometimes neurological symptoms are detected already at birth.

Current experience in treating children with intraspinal tumor extension reveals no advantages of surgical spinal cord decompression over chemotherapy [62]. The mere presence of a tumor in the spinal canal, verified by MRI, whether asymptomatic or with signs of spinal cord compression, is not yet an absolute indication to change the therapeutic strategy described in section 3 of these guidelines and to proceed with its immediate surgical removal. If the patient's neurological status is stable (with no significant difference whether it is stably good or stably bad), removing the intraspinal tumor component is not mandatory. This issue should be discussed with a pediatric oncologist, and chemotherapy may most often be the method of choice. Neurosurgical intervention is certainly indicated if there is a rapid (within days, weeks) progression of neurological deficit. In this case, the rate of decompression plays an important role. Surgery is indicated if it is known that this tumor variant does not require chemotherapy and, according to the protocol, the patient's treatment is surgical only. Surgery may be considered as a first option when a tissue sample is required to determine the histological type of tumor and surgical intervention must be performed anyway as an alternative to laparotomy or thoracotomy. Neurosurgical treatment may also be performed in case of neurological deterioration after the initiation of chemotherapy or during active surveillance.

The decision regarding the need for neurosurgical intervention is made by a multidisciplinary team involving a pediatric oncologist, neurosurgeon, neurologist, and radiologist.

The decision favoring surgery is made in the event of negative dynamics in the child's neurological status. If the neurological status is stable, chemotherapy is preferred.

The surgery is performed by a pediatric neurosurgery specialist. The patient's position on the operating table is supine or lateral. Bone-plastic laminotomy rather than laminectomy is preferred, with subsequent restoration of the bone block of the spinous processes and posterior vertebral arches. Tumor removal is performed using microsurgical techniques within the visible margins of the tumor. If there is a risk of damaging nerve roots or the spinal cord, tumor fragments may be left behind to avoid compromising the integrity of neural structures.

1.3. Management of patients under observation (low risk) upon disease progression/relapse

In case of detecting local relapse in low-risk patients after regression of the primary tumor, it is necessary to consider repeat biopsy and further workup (see sections 2.3, 2.4, 2.5). If the histological report is neuroblastoma, consider initiating chemotherapy; if the histological report is ganglioneuroma or mixed ganglioneuroblastoma, consider repeat surgery.

In case of continuous slow asymptomatic enlargement of the residual tumor component in patients under observation, repeat biopsy and further workup may be considered (see sections 2.3, 2.4, 2.5). If the histological report is neuroblastoma, consider initiating chemotherapy; if the histological report is ganglioneuroma or mixed ganglioneuroblastoma, consider repeat surgery.

In case of transformation to stage 4, the treatment volume depends on the patient's age. Further workup should be considered (see sections 2.3, 2.4, 2.5). In case of confirmed transformation to stage 4 in patients under 1 year of age, intensive chemotherapy is recommended within the framework of recommendations for intermediate-risk patients; in patients over 1 year of age, therapy follows the high-risk patient treatment protocol.

In case of progression in patients under observation within stage 4S, management tactics are determined based on the clinical status and the presence/development of life-threatening symptoms (LTS). When LTS develop, chemotherapy according to the N4 regimen is indicated (no more than 4 courses).

In the cohort of patients with stage 4S neuroblastoma, the general treatment concept corresponds to that of patients with stages 1-3. The main principle underlying the treatment concept is maximum therapy de-escalation. It should be noted that an important characteristic of the tumor in stage 4S neuroblastoma is its ability to progress followed by spontaneous regression. Moreover, progression can be driven by both an increase in the size of the primary focus/foci and an increase in the number and size of metastatic lesions, predominantly in the liver, leading to massive hepatomegaly. Growth of the primary tumor, increased liver involvement, or skin metastases without clinical deterioration do not require special treatment. The indication for chemotherapy according to the N4 regimen is the development of clinically significant LTS. Therapy is carried out until the induction of tumor regression and resolution of LTS are confirmed. Response to therapy is assessed after each course of chemotherapy. The maximum number of treatment courses is 4.

Comments: administering radiation therapy in this category of patients requires exceptional coordination among the entire radiation therapy department team, including scheduling time for timely topographic and tomimetric planning of radiation therapy. Provisions must be made to free up the physician for rapid contouring of the liver and kidneys, as well as the medical physicist for treatment plan calculation.

CT marking and subsequent irradiation sessions are recommended to be performed while the child is in natural sleep. As a rule, general anesthesia is not required for this.

Topometry is performed using a vacuum immobilization mattress. 

The gross tumor volume (GTV) corresponds to the clinical target volume (CTV) and includes the entire liver parenchyma. The PTV margin is 4–5 mm. Contouring of the kidneys is also required to reduce the radiation dose to them when calculating the treatment plan.

The planned fractional dose (FD) is 1.5 Gy, with a total dose (TD) of 4.5–6 Gy delivered in 3–4 daily fractions.

Since the situation requires immediate initiation of therapy, planning and the start of irradiation must be performed on the same day. It is acceptable to perform the first session using a "simple" irradiation technique, for example, using two lateral fields while excluding the renal parenchyma from the treatment fields. For subsequent sessions, a more adequate technique in terms of target coverage should be selected, applying conformal external beam radiotherapy, including IMRT (VMAT).

Based on the child's condition, after a joint multidisciplinary discussion, treatment breaks of one to two days are permissible to allow the radiation effect to manifest.

This therapeutic option is optional and depends on the severity of the child's condition, equipment availability, and the medical organization's expertise.  Determining final indications requires consultation at a federal/national center.

1.4. Follow-up monitoring of surveillance group (low-risk) patients.

• clinical examination (see section 2 of these recommendations);

• tumor markers (see section 2 of these recommendations);

• MRI/MSCT of the affected anatomical region with contrast enhancement;

• MIBG scintigraphy or FDG-PET/CT (in case of initial MIBG-negative tumor status) or other radioisotope methods previously used at initial diagnosis (if uptake was noted before surgery) for surveillance group patients 3 months after surgery or completion of chemotherapy.

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

• clinical examination (see section 2 of these recommendations) – before each cycle of N4 or #carboplatin**/etoposide**;

• tumor markers (see section 2 of these recommendations) – before each cycle of N4;

• ultrasound of the primary tumor and metastasis sites – before each cycle of N4 or #carboplatin**/etoposide**;

• ECG/EchoCG – before each cycle of N4;

• MRI/MSCT of the affected anatomical region with contrast enhancement – after each course of N4 or #carboplatin**/etoposide** or earlier if necessary;

• ¹²³I-MIBG scintigraphy or PET/CT with FDG, or other radioisotope imaging methods described in the «diagnostics» section (depending on which method was used at the time of diagnosis, though 123I-MIBG scintigraphy should be preferred) – after the last course of N4 or #carboplatin**/etoposide** or earlier if necessary;

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

Comments: if recurrence or progression is detected during follow-up, the results can be compared with the postoperative status.

2. Treatment of intermediate-risk patients

Comments: during preoperative planning, tumor topography and its relationship with surrounding anatomical structures (major vessels, parenchymal organs) are evaluated (image-defined risk factors - IDRFs). Complete resection is indicated only if the estimated risk of postoperative complications is low. Surgery should not be mutilating (e.g., nephrectomy). If the estimated risk of complications is high, only a biopsy is permissible.

Following the initial surgical intervention and pathomorphological examination of the surgical specimen, the disease stage is finally verified according to the INSS system.

When planning surgical treatment, the assessment of image-defined risk factors (IDRFs) is mandatory. Surgical intervention aimed at removing the primary tumor is usually delayed (second-look surgery). Prior PCT aims to reduce the primary tumor size in order to increase the frequency of macroscopically complete resection, decrease the risk of surgical complications, and reduce the risk of intraoperative rupture. Delayed surgery is recommended after the 4th, 5th, or 6th course of induction PCT. The extent of surgery is determined after joint discussion by pediatric oncologists, surgeons, and imaging specialists. During preoperative planning, the relationship of the tumor with vital structures is evaluated. The risk of surgery must be balanced against the benefit of radical primary tumor removal. Microscopically radical tumor removal is not required. The presence of microscopically or even macroscopically residual tumor is acceptable.

Since surgery following radiation therapy may be complicated by the development of post-radiation fibrosis, an attempt at tumor resection is planned prior to radiation therapy. It should be noted that since tumor rupture is less likely after chemotherapy, loss of tumor integrity during second-look surgery is acceptable and may facilitate complete resection.

Comments: criteria for initiating a PCT course:

●                   leukocytes > 2000/µL;

●                   lymphocytes > 1000/µL;

●                   platelets > 50,000/µL;

●                   no signs of infection.

If these criteria are not met, the start of the chemotherapy course is postponed. If the delay exceeds 7 days or there is an ongoing infectious episode of ≥ grade III severity, drug doses in the subsequent cycle are modified.

Comments: the cumulative dose of doxorubicin** should not exceed 180 mg/m² to reduce the risk of delayed cardiotoxicity.

Comments: differentiation therapy with #isotretinoin is administered, starting 21 days after the start of the last course of the N7 regimen. #Isotretinoin is prescribed at a dose of 160 mg/m² divided into 2–3 doses for 14 days, followed by a 14-day break, after which the next cycle begins. After 6 cycles of therapy, a 3-month break is provided, followed by another 3 courses of #isotretinoin therapy in the same regimen. Thus, a total of 9 courses of #isotretinoin therapy are administered [13, 39, 44].

The drug should be taken with fatty food (milk).

Cycle initiation criteria: absence of infection foci, absence of mucositis and dermatitis, leukocytes > 1 × 10⁹/L, liver toxicity no higher than grade 2, normal serum calcium levels. During therapy, it is recommended to monitor the complete blood count, biochemical blood test (electrolytes, necessarily calcium, liver enzymes, bilirubin, urea, creatinine, triglycerides) on days 1, 8, and 15 of the course. If hypercalcemia > 3.0 mmol/L develops, #isotretinoin is discontinued.

Excessive sun exposure is contraindicated during #isotretinoin therapy. In case of dermatitis, skin care with products containing alpha-tocopheryl acetate should be used; if ineffective, topical corticosteroids for skin diseases should be applied.

The decision on differentiation therapy with #isotretinoin for patients with intermediate-risk NB remains at the discretion of the center treating the patient.

Comments: a metabolically active residual tumor is defined as:

• a residual tumor accumulating a radiopharmaceutical during 123I-MIBG scintigraphy (provided the tumor was initially MIBG-positive) or 18F-FDG PET/CT (provided the tumor was initially MIBG-negative or initial 18F-FDG PET/CT was performed) or other radioisotope methods (provided these radioisotope methods were performed at diagnosis);

• unequivocal contrast enhancement on MRI (only for tumors that were completely negative on initial 123I-MIBG scintigraphy).

A residual metabolically inactive tumor in the absence of objective signs of progression according to CT, MRI, or ultrasound does not require external beam radiation therapy.

Requirements for RT and specifics of RT in patients with neuroblastoma can be found in Section 7.5 of these guidelines.

• evaluation of NSE levels (after each course of induction, maintenance, and #isotretinoin therapy);

• ultrasound of the affected area after each course of induction therapy, after the 2nd and 4th courses of maintenance therapy, and then every 6 weeks during #isotretinoin therapy;

• MSCT/MRI of the affected anatomical region after the 2nd, 4th, and 6th courses of induction therapy, after the 2nd and 4th courses of the N7 regimen, then after the 3rd, 6th, before the 7th, and after the 9th courses of #isotretinoin therapy;

• MIBG scintigraphy and/or FDG PET/CT and/or other radioisotope imaging methods (see above) after 6 courses of induction therapy, after maintenance therapy, and after the end of therapy (the radioisotope diagnostic method can be chosen depending on which method was used at diagnosis, but MIBG scintigraphy should be preferred);

• bone marrow status assessment (4-site myelogram and, for children older than 12 months, additionally 2-site trephine biopsy) (in patients under 1 year of age with stage 4 disease and bone marrow involvement) after the 2nd (in all patients), 4th (in the absence of clearance after the 2nd course), and 6th courses, and before the completion of therapy.

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

Comments: monitoring of chemotherapy side effects includes evaluation of complete blood count, urinalysis, and general biochemical blood test before each course of therapy. Echocardiography is performed before courses containing doxorubicin**. Before courses containing cisplatin**, the glomerular filtration rate is estimated using the Schwartz formula (Schwartz G.J., 1987) or by measuring blood cystatin C levels. Given the potential for renal tubular damage in patients receiving #ifosfamide**, tubular dysfunction based on fractional phosphate reabsorption was monitored prior to drug administration. Before #isotretinoin courses, serum calcium and triglyceride levels are evaluated.

3. Treatment of high-risk patients

Comments: during preoperative planning, tumor topography and its relationship with vital structures (great vessels, parenchymal organs) are assessed (image-defined risk factors – IDRF). Complete resection is indicated only if the estimated risk of postoperative complications is low. The surgery should not be mutilating (e.g., nephrectomy). In patients with distant metastases at diagnosis meeting stage 4 INSS criteria, performing only tumor biopsy is preferable to initiate systemic chemotherapy as early as possible.

Surgical intervention aimed at removing the primary tumor is generally delayed (second-look surgery). Prior chemotherapy is intended to reduce the size of the primary tumor in order to increase the rate of its macroscopically complete resection, reduce the risk of surgical complications, and lower the risk of intraoperative rupture. Delayed surgery is recommended after the 4th, 5th, or 6th course of induction chemotherapy. The scope of surgery is determined after a joint discussion among pediatric oncologists, surgeons, and imaging specialists. Preoperative planning involves assessing the relationship of the tumor with vital structures (great vessels, parenchymal organs, etc.) and determining IDRF surgical risk factors. Patients with a localized tumor up to 7 cm in the retroperitoneal region and up to 9 cm in the posterior mediastinum, in the absence of surgical risk factors—specifically, no total involvement of the main artery in the tumor and preserved lumen of the main vein—may be candidates for minimally invasive surgery. In the presence of surgical risk factors, namely tumor involvement of the great vessels and tumor invasion into adjacent organs, open surgery is recommended. In such cases, standard surgical interventions include laparotomy, thoracotomy, and combined approaches that provide maximum visualization of the surgical field. The surgical team must have extensive experience, proficiency in precision microsurgical techniques and reconstructive surgery, and the use of magnifying optics is mandatory. The goal should always be maximum tumor removal while simultaneously preventing the risk of postoperative complications, which can significantly delay chemotherapy and worsen the patient's prognosis. Ultra-radical surgeries in patients with multiple surgical risk factors frequently lead to complications, primarily impaired blood supply to internal organs.

Since performing surgery after a course of radiation therapy may be complicated by the development of post-radiation fibrosis, an attempt at tumor resection is planned prior to radiation therapy. It should be noted that since tumor rupture is less likely after chemotherapy, a breach of tumor integrity during second-look surgery is acceptable and may facilitate complete resection.

Comments: criteria for initiating a PCT course:

●                   leukocytes > 2000/µL;

●                   lymphocytes > 1000/µL;

●                   platelets > 50,000/µL;

●                   no signs of infection.

If these criteria are not met, the start of the chemotherapy course is postponed. If the delay exceeds 7 days or there is an infectious episode of ≥ grade III severity, or other types of severe organ toxicity, the drug doses in the subsequent cycle are modified by 25–50%.

Patients aged over 18 months to 18 years with a diagnosis of high-risk neuroblastoma or ganglioneuroblastoma with stage 4 disease according to INSS may be eligible for two standard courses of induction chemotherapy according to the N5 and N6 regimens, followed by 4 courses of similar chemotherapy combined with anti-GD2 monoclonal antibodies ch14.18/CHO (dinutuximab beta)—courses N5-Q and N6-Q (for course regimens, see Appendix A3.2, Appendix B, Fig. B4) [46]. Delayed surgery may be performed after the 4th or 6th course of induction therapy, and hematopoietic stem cell apheresis may be performed after the 2nd–5th courses of induction therapy. This type of therapy may be performed only in specialized medical institutions with extensive experience in monoclonal antibody immunotherapy and after receiving a multidisciplinary team consultation at a national/federal center.

Comments: the cumulative dose of doxorubicin** should not exceed 180 mg/m² to reduce the risk of delayed cardiotoxicity.

Comment: in patients in whom bone marrow clearance is not achieved after the 4th course of induction therapy, peripheral stem cell apheresis may be performed after the 5th course.

Comments: it is critically important for ensuring the timely execution of high-dose therapy and auto-HSCT to notify the transplantation center about a patient with high-risk neuroblastoma at the time of diagnosis and initiation of special treatment.

Conditioning regimens include #carboplatin**/etoposide**/melphalan** or #treosulfan/melphalan** or busulfan**/melphalan** regimens, at the discretion of the clinic performing auto-HSCT [48-51, 93]. If a busulfan-containing regimen is used, it is necessary to include an anticonvulsant in the supportive care regimen to prevent neurotoxicity [92]. Single or tandem high-dose chemotherapy and auto-HSCT may be performed (at the discretion of the transplant center). The choice of high-dose chemotherapy regimens for tandem auto-HSCT is carried out in accordance with the internal guidelines of the clinic performing tandem auto-HSCT. Conditioning regimens used in tandem auto-HSCT include #carboplatin**/etoposide**/melphalan** or #treosulfan/melphalan** or busulfan**/melphalan** or #thiotepa**/cyclophosphamide** or #thiotepa** regimens, at the discretion of the clinic performing auto-HSCT [74-75, 86]. If the HSCT procedure is performed by a transplantation department that is not part of a federal center specializing in pediatric HSCT, coordination of the management strategy with a national/federal center is recommended. High-dose therapy regimens are described in Appendix A3.1.

Decontamination is not performed. Antibacterial, antiviral, and antifungal therapy, supportive and infusion therapy, antiemetic therapy, administration of colony-stimulating factors, and laboratory monitoring of the patient's condition are carried out in accordance with the local protocol of the transplantation center [13].

Criteria for performing auto-HSCT:

• complete blood count: leukocytes > 2000/µl, lymphocytes > 1000/µl, platelets > 50,000/µl;

• ototoxicity < grade II (i.e., loss ≤ 30 dB at 2 kHz, audiometry required);

• creatinine ≤ 150% of the upper limit of normal, endogenous creatinine clearance ≥ 70 ml/min × 1.73 m²;

• hepatotoxicity level < grade II

• cardiomyopathy < grade I (according to echocardiography and ECG);

• absence of signs of severe infection (sepsis, septic shock) for 14 days (afebrile state, no foci of infection, complete stabilization of the condition);

• presence of a central venous catheter of the Certofix, Broviac, Hickman, Port-A-Cath systems.

• absence of disease progression according to a comprehensive examination performed after the induction therapy phase.

Required:

• perform mobilization, harvest, and CD34+ selection of ≥ 2 × 10⁶/kg (see the relevant protocol);

• prepare the patient;

• prepare the isolation room;

• prepare the accompanying person (the child's parents or another person authorized by the parents via a notarized power of attorney, with informed consent).

Criteria for graft engraftment:

• granulocytes > 500/µL;

• leukocytes > 1000/µL;

• platelets > 30/µL provided there have been no platelet concentrate transfusions within the last 3 days.

Comments: following graft engraftment on day +30 after the myeloinfusion procedure, initiation of differentiation therapy with #isotretinoin is planned, administered at a dose of 160 mg/m² in 2–3 divided doses for 14 days followed by a 14-day break, after which the next cycle begins. Following 6 cycles of therapy, a 3-month break is provided, followed by another 3 courses of #isotretinoin therapy in the same regimen. Thus, a total of 9 courses of #isotretinoin therapy are administered. Differentiation therapy may or may not be performed at the discretion of the medical institution treating the given patient. In the case of anti-GD2 antibody immunotherapy performed in accordance with the timelines established by these guidelines (60–100 days from the day of auto-HSCT), the cycle of differentiating therapy may be paused for the duration of the immunotherapy at the discretion of the center performing the immunotherapy.

The drug should be taken with fatty food (milk).

Cycle start criteria: absence of infectious foci, absence of mucositis and dermatitis, leukocytes > 1×10⁹/L, hepatic toxicity no higher than grade 2, normal serum calcium levels. During therapy, monitoring of the complete blood count, blood chemistry (electrolytes, mandatory calcium, liver enzymes, bilirubin, urea, creatinine, triglycerides) is recommended on days 1, 8, and 15 of the course. If hypercalcemia > 3.0 mmol/L develops, 13-cis-retinoic acid is discontinued.

Excessive sun exposure is contraindicated during #isotretinoin therapy. In case of dermatitis, skin care with vitamin E products should be used; if ineffective, corticosteroid ointments should be applied.

Comments: a metabolically active residual tumor is defined as:

● residual tumor accumulating the radiopharmaceutical during MIBG scintigraphy (provided the initial tumor was MIBG-positive) or FDG PET/CT (provided the initial tumor was MIBG-negative or initial FDG PET/CT was performed) or other radioisotope imaging methods (provided they were performed at initial diagnosis);

● unequivocal contrast enhancement on MSCT/MRI (only for tumors that were entirely negative on initial MIBG scintigraphy).

Residual metabolically inactive tumor with no signs of progression on MSCT, MRI, or ultrasound does not require radiation therapy.

Radiation therapy is recommended after auto-HSCT and achievement of graft engraftment. Given the necessity of starting #isotretinoin therapy on day +30 post-auto-HSCT and the potential for increased radiation reactions due to concurrent radiation therapy and 13-cis-retinoic acid intake, radiation therapy is performed after the first course of differentiation therapy. The minimum interval from 13-cis-retinoic acid administration to the start of radiation therapy is 7 days. Differentiation therapy is resumed 7–10 days after the completion of the radiation therapy course.

An exception is made for patients who received high-dose therapy according to the BuMel regimen. If there are indications for external beam radiotherapy (EBRT), the latter should be postponed for at least 60 days from the date of auto-HSCT, considering the potential potentiation of radiation reactions by busulfan**.

If it is impossible to ensure tolerant doses to healthy structures during radiation planning in this regimen, a total dose (TD) of 21 Gy with a fractional dose (FD) of 1.5 Gy is recommended.

Planning and principles of EBRT in high-risk patients correspond to those in intermediate-risk patients. Details are presented in the section "External beam radiotherapy in intermediate-risk patients".

Within the framework of the original NB-2004 protocol recommendations, irradiation of metastatic lesions (even metabolically active ones) is not performed in routine practice.

However, in the case of a persistent solitary metabolically active lesion confirmed by CT/MRI, MIBG scintigraphy, FDG PET/CT, or other radioisotope imaging methods, local radiation therapy may be considered as an additional therapeutic option. Indications for EBRT are determined strictly individually by a medical board (consilium).

Fractional doses (FD) of 1.5–1.8 Gy and a total dose (TD) of 21 Gy are used, depending on the localization and proximity of critical structures.

Comments: The use of dinutuximab beta antibodies is indicated as 5 cycles with an interval of 36 days between courses. The drug is administered as a continuous infusion for 10 days. The total cumulative dose per course is 100 mg/m², with a single daily dose of 10 mg/m²/day. A total of 5 courses of immunotherapy are planned. The optimal timeframe to initiate immunotherapy is 60–100 days after auto-HSCT, depending on the patient's performance status, hematopoietic recovery, and the timing of radiation therapy. On day 11 of the first course of dinutuximab beta immunotherapy, the next course of #isotretinoin begins (14 days) for patients undergoing differentiation and immunotherapy (determined by the healthcare facility treating the patient). This is followed by a 14-day break. Subsequently, the second cycle of dinutuximab beta immunotherapy is administered, starting with the infusion of dinutuximab beta (IV 10 mg/m²/day) for 10 days, and so on. After completing 5 courses of immunotherapy (by which time 6 courses of #isotretinoin therapy have been administered), a 3-month break is recommended, followed by 3 additional courses of #isotretinoin therapy. The dose of dinutuximab beta is calculated based on the patient's body surface area or body weight:

●                 Patients with a body weight >12 kg: the dose of dinutuximab beta is calculated according to body surface area as 10 mg/m²/day. The total dose of dinutuximab beta administered per cycle is 100 mg/m² of body surface area.

● Patients with a body weight <12 kg and >5 kg: calculation of the dinutuximab beta dose is based on body weight (kg)—0.33 mg/kg/day. The total dose of dinutuximab administered per cycle is 3.3 mg/kg of body weight.

Criteria for starting a course of dinutuximab beta immunotherapy:

• Satisfactory general condition (Lansky or Karnofsky scale > 70)

• Absence of clinical manifestations of an infectious process (skin, lips, and mucous membranes are intact)

• Absence of signs of drug-induced neuropathy or neuropathic pain

• Adequate bone marrow function: absolute neutrophil count ≥500/µL, platelet count ≥20,000/µL, hemoglobin >8.0 g/dL.

• Adequate renal function: creatinine clearance or glomerular filtration rate (GFR) >60 mL/min/1.73 m².

• Coagulation parameters (PT 70-120%, aPTT < 36 sec).

• Absence of clinical signs of heart failure, EF (ejection fraction) ≥55%

• Assessment of the respiratory system function (pulse oximetry O2 saturation > 94% on room air, no respiratory disorders at rest), absence of abnormalities on chest X-ray.

• No progression of the underlying disease

Route of administration.

●                 A mandatory prerequisite for initiating dinutuximab beta therapy is the presence of an adequately functioning central venous catheter (preferably double-lumen).

●                 Dinutuximab beta is intended for intravenous infusion. The solution must be administered via a central vein. Other simultaneously administered intravenous medications must be delivered through a separate infusion line.

For continuous infusions, the solution is administered at a rate of 2 ml per hour (48 ml per day) using an infusion pump.

• assessment of NSE levels after each course of induction therapy, autologous HSCT, and each course of #isotretinoin therapy, and prior to the completion of therapy;

• ultrasound of the affected area after each course of induction therapy, autologous HSCT, and subsequently every 6 weeks during #isotretinoin therapy and prior to the completion of therapy;

• MSCT/MRI of the affected anatomical region after the 2nd, 4th, and 6th courses of induction therapy, subsequently at 3, 6, and 9 months from the time of autologous HSCT, and prior to the completion of therapy;

• MSCT of the chest and abdomen with contrast enhancement after the 2nd, 4th, and 6th courses of induction therapy, subsequently at 3, 6, and 9 months from the time of autologous HSCT, and after the completion of therapy;

• brain MRI with contrast enhancement after the 6th course of induction therapy, before the start of immunotherapy, and subsequently every 6 months and prior to the completion of therapy;

• scintigraphy with ¹²³I-MIBG (or other radioisotope diagnostic methods (see above)) after the 4th and 6th courses of induction therapy, 3 months after autologous HSCT (in case of persistent pathological uptake in the previous study), and subsequently every 6 months until normalization; prior to the completion of therapy;

• bone marrow status assessment (myelogram from 4 sites and, for children older than 12 months, additionally trephine biopsy from 2 sites) (in patients with bone marrow involvement) after the 2nd course (in all patients) in the absence of clearance after 2 courses, after the 4th course of therapy (in the absence of clearance after the 2nd course), after the 6th course of therapy (in all patients), 3 months after autologous HSCT (in the absence of clearance prior to HSCT), and prior to the completion of therapy.

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

Comments: Monitoring of chemotherapy side effects includes evaluation of complete blood count, urinalysis, and general biochemical blood test before each course of therapy. Before courses containing doxorubicin**, echocardiography is performed. Before courses with cisplatin**, the glomerular filtration rate is assessed using the Schwartz formula or by serum cystatin C levels. Considering the potential for renal tubular damage in patients receiving #ifosfamide**, tubular dysfunction monitoring based on the evaluation of fractional phosphate reabsorption was performed prior to drug administration. Prior to #isotretinoin therapy courses, serum calcium and triglyceride levels are evaluated. After the induction therapy stage, hearing assessment was performed using auditory evoked potential technology or audiometry.

4. Treatment of relapses/disease progression

Comments: As part of the evaluation, the following laboratory tests are recommended: complete blood count (CBC), general biochemical blood test, coagulogram, AB0 blood group typing, Rh(D) antigen determination, urinalysis, serum ferritin and neuron-specific enolase levels, and—if feasible—catecholamine metabolite levels (HVA and VMA); instrumental diagnostic methods (ultrasound of the abdominal cavity and other involved areas, chest radiography and/or MSCT and/or MRI); bone marrow examination; ¹²³I-MIBG scintigraphy or 18F-FDG PET/CT, or other radioisotope imaging methods. If technical capabilities for ¹²³I-MIBG scintigraphy or 18F-FDG PET/CT are lacking, but there is compelling evidence of disease relapse (based on imaging, bone marrow examination, etc.), these studies may be performed at later stages following the completion of one of the treatment courses. The investigations are carried out in accordance with the recommendations for initial staging (Sections 2.3–2.5). To verify potential CNS involvement, contrast-enhanced brain MRI is recommended, along with contrast-enhanced spinal MRI when indicated. In the presence of neurological symptoms or when brain/spinal cord lesions are detected on imaging, a lumbar puncture with cerebrospinal fluid (CSF) cytological and, if indicated, bacteriological examination may be recommended. If a soft-tissue component is accessible for biopsy and significant surgical risks are absent, morphological verification of the relapse is possible. In cases where soft-tissue biopsy carries surgical risks, initiating therapy based on imaging and laboratory findings is acceptable.

The choice of salvage therapy regimen is made in accordance with the clinic's internal guidelines. A change of salvage therapy regimen is possible in case of toxicity that prevents subsequent treatment courses (e.g., irinotecan-associated diarrhea, hematological toxicity, etc.), lack of treatment response, or further disease progression. The next course starts on the 21st day from the first day of the previous course.

Criteria for initiating a polychemotherapy course:

●                   leukocytes > 2000/µL;

●                   lymphocytes > 750/µl;

●                   platelets > 50,000/µL;

●                   no signs of infection.

If these criteria are not met, the start of the polychemotherapy course is delayed. If the delay exceeds 7 days or an infectious episode of ≥ grade III severity occurs, drug doses in the subsequent cycle are modified (a dose reduction of 25-50% is permissible).

Evaluation of the efficacy of salvage therapy is performed every 2-4 courses of second-line (or third-line and subsequent, in case of switching to another therapy regimen due to toxicity or treatment failure) therapy. It is recommended to discuss further stages of therapy (consolidation and post-consolidation) with a national/federal center.

The following salvage chemotherapy options may be used: #irinotecan** and #temozolomide**; #irinotecan**, #temozolomide** and bevacizumab**; #topotecan** and #temozolomide**; #topotecan** and cyclophosphamide**, chemoimmunotherapy (polychemotherapy + dinutuximab beta), RIST, metronomic therapy (see treatment regimens in Appendix A3.2).

Comments: This treatment method may be used prior to the initiation of systemic anti-relapse therapy in cases of symptomatic involvement requiring emergency intervention (e.g., CNS relapse). In the presence of asymptomatic lesions or the detection of additional lesions outside the CNS, surgical treatment is coordinated with a national/federal center.

Placement of an Ommaya reservoir with intraventricular administration of chemotherapy drugs (etoposide**, #topotecan**) is permissible for patients with metastatic CNS relapse. Therapy may be administered concurrently with systemic therapy (chemotherapy, chemo-immunotherapy, targeted therapy). The treatment regimen is coordinated with a national/federal center.

Upon achieving stabilization, partial, or complete response based on interim staging performed after 1-5 courses of systemic therapy, the use of chemo-immunotherapy is permissible. The treatment regimen is coordinated with a national/federal center.

Upon achieving a complete response of CNS lesions and a complete or partial response of extra-CNS lesions (if present), the use of consolidation and maintenance therapy methods is recommended (repeat auto-HSCT [more preferred in late relapse], allogeneic HSCT, #temozolomide** monotherapy, metronomic therapy, immunotherapy, chemo-immunotherapy). The treatment regimen must be coordinated with a national/federal center.

Treatment of patients within clinical trials is permitted provided that the treatment methods proposed within the trial do not contradict these recommendations.

5. Nutritional support

Nutritional support is provided by prescribing specialized enteral nutrition products. Enteral nutrition food products or therapeutic nutritional formulas are liquid or dry (reconstituted to ready-to-use) dietary medical or dietary prophylactic food products intended for oral consumption directly or via a feeding tube when the body's requirements for nutrients and energy cannot be met in the usual manner [108]. Therapeutic formulas are specially designed food products with a defined chemical composition, energy value, physical properties, and proven therapeutic effect, meeting the physiological needs of the body and taking into account the metabolic disorders of the sick person [109]. When choosing the form, method, type, and volume of nutritional support, it is recommended to be guided primarily by the principle of an individual patient-oriented approach, in accordance with the clinical situation and logic [110, 111]

In obese patients (with excess fat mass), hidden protein-energy malnutrition may develop, characterized by a deficiency in fat-free body mass and a critical reduction of its skeletal muscle compartment; therefore, correction of this type of deficiency is recommended, and the presence of obesity per se is not a contraindication for enteral or parenteral nutritional support [111-113].

Comment: total energy expenditure (TEE) is calculated using the formula: TEE = BEE × CF, where BEE is basal energy expenditure and CF is the conversion factor. The gold standard for determining BEE is indirect calorimetry. If indirect calorimetry is not feasible, BEE can be calculated using a formula (e.g., Schofield) [15]. To avoid overfeeding in the initial stages of nutritional support in children with chronic protein-energy malnutrition and/or a history of suspected nutrient intake deficiency for 3 or more consecutive months, a CF of 0.85–1.4 is used to calculate TEE. The exact volume of nutritional intervention is determined based on the specific clinical situation.

Comment: EN is the most physiological method, providing intraluminal trophism of the gastrointestinal mucosa, preventing microbial translocation from the intestinal lumen into the bloodstream, and being more cost-effective than parenteral nutrition

Comment: lack of appetite, refusal to eat and EN formulas, swallowing disorders, and the inability to meet nutrient and energy needs orally are indications for EN via a nasogastric tube. The presence of pathological conditions in which the patient must not take food naturally (acute pancreatitis, gastric outlet stenosis, high proximal fistulas) indicates the use of EN via a nasojejunal tube.

Comment: if the need for prolonged enteral nutrition is identified and there is a predicted risk of nutritional deficiency (including during chemoradiotherapy), preventive gastrostomy placement is possible, bypassing the tube feeding stage.

Comment: formulas are divided by their energy density into isocaloric (1 kcal/ml for children over one year and 0.67-0.69 kcal/ml for children under one year) and hypercaloric (more than 1 kcal/ml for children over one year, and 1 kcal/ml for children under one year). It is advisable to start nutritional support, especially in children with a history of or current gastrointestinal disorders and/or who have never received enteral nutrition before, with isocaloric formulas.

Comment: formulas are classified by chemical composition into polymeric (based on intact protein) and oligomeric (containing protein hydrolysates) or semi-elemental. Elemental formulas do not contain intact protein; their protein component is represented by amino acids. Typically, elemental formulas are prescribed for diagnosed cow's milk protein allergy.

Comments: the key indication for prescribing parenteral nutrition (PN) is the inability to meet the estimated nutritional requirements (at least at the level of basal energy expenditure) enterally – either currently or potentially in the short term.

Comments: initiating parenteral nutrition immediately at full volume is highly discouraged, as is a one-time discontinuation ("starting the next day") of total parenteral nutrition. It is especially dangerous to prescribe full parenteral nutrition to patients with a prolonged lack of alimentation due to the possible development of refeeding syndrome. The volume of PN should be gradually (stepwise) increased with parallel monitoring of blood acid-base balance, electrolytes, glucose, urea, and direct bilirubin. If necessary, the volume and composition of PN must be adjusted.

For tables, see Appendix A.4..

6. Infectious complications and supportive care.

Infectious complications continue to be the leading cause of morbidity and mortality in patients with malignancies during the period of chemotherapy and hematopoietic stem cell transplantation (HSCT) [120]. Competent and rational prescription of antimicrobial drugs is the key to successful therapy for both infectious complications and the underlying disease, as it allows chemotherapy to be administered in full doses and while maintaining the schedule [121, 122]. Over the past decade, the problem of infections caused by antibiotic-resistant microorganisms, including reserve-group drugs, has become increasingly global [123]. As a result, even commonplace infections are becoming life-threatening due to extremely limited treatment options. The implementation of diagnostic standards, antibacterial and antifungal therapy are significant elements of supportive care.

The high-risk group includes patients with a granulocyte count of <0.5×10⁹/L and a duration of neutropenia of more than 7 days; patients with an expected duration of neutropenia of less than 7 days belong to the standard-risk group. .

In patients with neutropenia due to impaired barrier function of the gastrointestinal mucosa, the phenomenon of translocation of the endogenous intestinal flora directly into the bloodstream may develop. During the development of an infectious episode, local clinical symptoms may be absent, and the only sign may be febrile fever/hypothermia, lethargy, or altered consciousness.

Comments: microbiological blood culture is performed before prescribing antibiotics. Blood is drawn from a centrally inserted venous catheter (CVC) or a peripherally inserted central catheter (PICC), and if neither is available, from a peripheral vein during a febrile spike, episode of hypothermia, chills and/or hemodynamic instability, or the appearance of septicopyemic foci. If the patient has a multi-lumen CVC and symptoms of catheter-related bloodstream infection, blood samples must be drawn from each lumen. Reliable results can be obtained by properly selecting the blood culture bottles and matching the required blood volume: for children up to 10–12 kg, 1–3 ml into pediatric bottles; for children over three years of age, 6–10 ml into aerobic bottles (it is optimal to use an automated blood culture analyzer). If an anaerobic etiology of the infection is suspected, samples are inoculated into anaerobic bottles; if fungal infection is suspected, into mycology bottles. To avoid contamination and misinterpretation, aseptic technique must be strictly observed during blood collection and inoculation. To increase the efficacy of blood culturing, a twofold or threefold blood draw is indicated during the first 24 hours of fever. After microorganism verification, subsequent blood cultures are performed 24–48 hours after initiating antibiotic therapy until the first negative blood culture is obtained. Repeat microbiological blood testing is necessary in case of persistent febrile neutropenia (FN) for 72 hours, as well as prior to the escalation of antibiotic therapy [129 - 132].

Comment: taking into account the growing incidence of antibiotic resistance, it is necessary to determine susceptibility, including to systemic reserve-group antibacterial drugs, as well as to determine resistance determinants.

Comments: microbiological studies are performed for precision antibiotic therapy during treatment in the presence of febrile fever and infectious complications.

Comment If signs of pneumonia are detected, tracheobronchoscopy and bronchoalveolar lavage (BAL) must be performed. The scope of the study should be maximal and, if necessary, include: molecular biological testing for respiratory syncytial virus, adenovirus, influenza viruses, metapneumovirus, parainfluenza viruses, rhinoviruses, bocavirus, coronaviruses, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Pneumocystis jirovecii, Mycobacterium tuberculosis complex, cytomegalovirus; microscopic examination of bronchoalveolar lavage fluid for fungi (yeast and mold) and Mycobacterium tuberculosis; microbiological (culture) testing for aerobic and facultatively anaerobic microorganisms, microbiological (culture) testing for fungi (yeast and mold), for Legionella pneumophila, and determination of fungal metabolites (galactomannan). BAL results obtained as soon as possible after the detection of lung lesions will have the highest diagnostic value [138–140].

It must be remembered that the results of X-ray examination of the lungs in neutropenic patients are unreliable and "lag behind" compared to multislice CT data. Radiography has low diagnostic capability and its performance is indicated only for the diagnosis of complications such as pneumothorax, hydrothorax, hydropericardium, as well as for monitoring the position of a CVC, pleural drains, or endotracheal tube [137, 141, 142].

Comment: depending on the clinical situation, echocardiography (to rule out endocarditis), duplex scanning of upper extremity veins in the projection of the CVC location (to rule out thrombotic deposits associated with the CVC), contrast-enhanced CT or MRI of the abdominal cavity, retroperitoneal space, and pelvis (to rule out damage to internal organs, intestines), esophagogastroduodenoscopy, and colonoscopy (to rule out erosive and ulcerative processes, pathological infiltration, and to identify a source of bleeding) are performed.

Other diagnostic studies

Comment: Respiratory viruses can be detected using either PCR or fluorescent antibody staining for antigen detection.

Comment: If bronchoscopy is not feasible, galactomannan testing can be performed on blood serum.

Comment: other methods, including DNA detection and microscopy, may also be used to detect Cryptococcus.

Due to the non-specific clinical and radiological presentation, the diagnostic workup for central nervous system infections should include invasive mycoses, toxoplasmosis, listeriosis, herpesviruses, and mycobacterioses (including atypical ones), in addition to cryptococcal infection.

Management of Febrile Neutropenia

Comments: Systemic antibacterial therapy should be prescribed immediately after blood collection for blood cultures, and administration must be intravenous only.

Parenteral antibiotics.

Comments: antimicrobial therapy is modified based on clinical symptoms, instrumental findings, and microbiological test results. If fever persists while the patient remains clinically stable, it is acceptable to wait 48–72 hours for a clinical response to initial antibacterial therapy, as fever is not the sole indicator of infection severity. First-line systemic carbapenems for febrile neutropenia are justified in patients with severe infections, involvement of the abdominal or perirectal regions, or the development of sepsis.

Comments on reserve antibacterial therapy:

· Colistimethate sodium – loading dose 100,000–150,000 IU/kg, maximum 9 million IU (equivalent to 8–10 mg/kg, maximum 720 mg) over 4 hours, followed by 50,000–75,000 IU/kg every 12 hours (maximum 9 million IU/day), equivalent to 4.5–6.5 mg/kg every 12 hours (maximum 360 mg q12h)

· Polymyxin B** 2.5 mg/kg/day divided into 2 doses; in children under 1 year of age, 4 mg/kg/day divided into 2 doses

· #Tigecycline** – loading dose 2 mg/kg (100 mg), followed by 1.2 mg/kg (50 mg) every 12 hours, primarily for complicated skin and soft tissue infections and complicated intra-abdominal infections

· #Ceftolozane/tazobactam** 3 g q8h or 120 mg/kg/day based on ceftolozane divided into 3 doses

· Ceftazidime + [avibactam**] 2.5 g q8h, or in children older than 3 months 150 mg/kg/day based on ceftazidime, or in children older than 3 months 120 mg/kg/day based on ceftazidime divided into 3 doses, each infusion lasting 2–3 hours. If #ceftazidime + [avibactam**] needs to be combined with #aztreonam**, the drugs must be administered simultaneously via parallel infusions.

When infections caused by gram-positive flora develop, the choice of antibacterial drugs should take into account susceptibility data and maximum efficacy for the specific clinical situation:

• For bloodstream infections, endocarditis, and device-related infections, preference should be given to agents with bactericidal activity against gram-positive microorganisms: vancomycin**, and in children older than 1 year, daptomycin** (8–10 mg/kg/day as a single daily dose) or ceftaroline fosamil** (600 mg q8h or 12 mg/kg q8h);

• In case of pneumonia, preference should be given to drugs with higher pulmonary bioavailability: linezolid** (600 mg q12h or 10 mg/kg q8h for children under 12 years of age), vancomycin**;

• In case of soft tissue involvement: linezolid**, daptomycin**, tigecycline**, vancomycin**

Empirical antifungal therapy

Comment to select empirical antifungal therapy, it is necessary to take into account prior antifungal prophylaxis—the dose of the drug, route of administration, and, if possible, serum drug concentrations. If oral formulations were previously administered and therapeutic blood concentrations were achieved, they should be discontinued and empirical therapy with systemic antifungals (from the echinocandin group or liposomal amphotericin B) initiated. If the concentration is found to be below the therapeutic range, oral formulations should be discontinued, and children older than two years should be prescribed intravenous voriconazole** to achieve an effective concentration. If persistent fever continues despite achieving therapeutic blood concentrations of voriconazole**, the strategy must be switched to empirical antifungal therapy. Empirical therapy should be continued until the resolution of agranulocytosis [165–168]. Amphotericin B deoxycholate is not used for empirical therapy in children.

Preemptive and targeted antifungal therapy

• All patients with febrile neutropenia and signs of invasive mycosis are recommended to receive preemptive antifungal therapy. This strategy is feasible only in clinics equipped to immediately perform a full range of diagnostic procedures (chest CT, bronchoscopy with subsequent bronchoalveolar lavage fluid analysis, and biopsy of affected organs and tissues when necessary) [137, 164–166].

GCE 5Level of Recommendation C (Level of Evidence 5)

Therapy of choice for candidemia/invasive candidiasis:

• Caspofungin at a dose of 70 mg/m2 on day 1 (maximum 70 mg/day), followed by 50 mg/m2/day (maximum 50 mg/day) for children older than three months

• Micafungin** 100 mg intravenously once daily or 2–4 mg/kg/day (in infants in the first month of life, the dose may be increased up to 10 mg/kg/day if CNS involvement is suspected)

• Anidulafungin** at a dose of 200 mg on the first day, followed by 100 mg once daily or 3 mg/kg on the first day, followed by 1.5 mg/kg/day for children older than one month (the drug of choice for patients with hepatic impairment)

• Amphotericin B [liposomal] 3 mg/kg/day

• Voriconazole** (for children aged 2–12 years weighing <40 kg, a loading dose of 18 mg/kg/day divided into 2 doses on day 1, followed by 16 mg/kg/day divided into 2 doses; for children >12 years, 12 mg/kg/day divided into 2 doses on day 1, followed by 8 mg/kg/day divided into 2 doses). Voriconazole** therapy must always be initiated intravenously.

GCE 5Level of Recommendation C (Level of Evidence 5)

Comments: if febrile patients with neutropenia are found to have lesions in the liver or other parenchymal organs, disseminated invasive candidiasis must be ruled out; it is treated with systemic antifungals (from the echinocandin group or lipid/liposomal formulations of amphotericin B).

Fluconazole** is not recommended for patients with neutropenia and/or hemodynamic instability [165].

Therapy of choice for invasive aspergillosis:

• In cases of invasive aspergillosis (IA), all patients with febrile neutropenia are recommended to start intravenous antifungal therapy immediately [165–171].

GCE 5Level of Recommendation C (Level of Evidence 5)

Comment:

• For children older than two years, the first-line drug is voriconazole** (treatment is always initiated with intravenous formulations, with subsequent transition to the oral route once the condition stabilizes, along with monitoring serum voriconazole concentrations to maintain them within the therapeutic range of 1.0–4.0 µg/mL) [167, 168];

• #Isavuconazole at a loading dose of 10 mg/kg q8h for two days (maximum 200 mg), followed by 10 mg/kg/day intravenously or orally for children aged 1 year and older; for children aged 6 months to 1 year, the single dose is 6 mg/kg (with the same administration schedule). Monitoring serum drug concentrations is not required. Due to the lack of pediatric labeling, it is a second-line therapy [233, 234];

• Amphotericin B [liposomal] at a dose of 3–5 mg/kg/day;

• Combination therapy: voriconazole**/amphotericin B [lipid complex] + another systemic antifungal agent (caspofungin**, micafungin**, anidulafungin)

Therapy is prescribed for a prolonged period (until risk factors resolve)—at least 12 weeks. If invasive aspergillosis develops during prior antifungal prophylaxis with triazoles and tetrazoles (voriconazole**, posaconazole), the drug class must be switched to a liposomal/lipid complex of amphotericin B. When CNS or renal involvement occurs, the drugs with the best bioavailability are voriconazole and #isavuconazole. If risk factors recur in a patient with a history of IA, secondary antifungal prophylaxis with the previously effective drug should be administered [167–171].

Therapy of choice for invasive mucormycosis:

• Amphotericin B [liposomal] at a dose of 5–10 mg/kg/day (maximum doses are recommended in case of cerebral involvement);

• #Isavuconazole at a loading dose of 10 mg/kg q8h for two days (maximum 200 mg), followed by 10 mg/kg/day. Monitoring serum drug concentrations is not required. Due to the lack of pediatric labeling, it is a second-line therapy [233, 234];

• Combination therapy with systemic antifungals: amphotericin B [liposomal] or [lipid complex] + posaconazole** or #isavuconazole +/- caspofungin** (for children older than three months) may be considered as salvage therapy (second-line therapy).

• Surgical intervention, multidisciplinary patient management approach.

• Posaconazole 15–20 mg/kg/day (up to 800 mg/day divided into 4 doses). Due to the need for therapeutic drug monitoring and highly variable pharmacokinetics, the tablet formulation is preferred. The drug is prescribed after the patient has stabilized, including for maintenance therapy and secondary prophylaxis.

7. Specific aspects of venous access to ensure successful diagnostic and therapeutic procedures in children

• Aseptic technique is recommended during the handling and care of venous catheters and the preparation of infusions [176].

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Comment:

Hand hygiene should be performed:

• before/after contact with the patient,

• before/after contact with invasive equipment, including infusion equipment,

• before/after procedures or manipulations with the catheter,

• after contact with surfaces in the ward,

• after contact with biological fluids,

• when moving from a more contaminated to a less contaminated area of the same patient,

• after removing gloves.

• catheter extension set – for catheter extension, working at a distance from the patient, catheter fixation, and clamp application,

• needleless connector – for closed-system infusion administration,

• infusion filters,

• three-way stopcock or manifold – to increase the number of infusion accesses, etc. [179].

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Comment: if the clamp on a CVC is lost or during prolonged use of a PVC, a clamp is required, which can be provided by using a catheter extension set. The catheter extension set also ensures the possibility of aseptic catheter application and the use of positive pressure technique when closing the catheter, which prevents blood reflux into the catheter.

Comment: the "chlorhexidine bath" is performed by daily wiping of the patient's skin with a 2% aqueous chlorhexidine bigluconate solution.

Infusion set.

- blood and blood components – upon removal/replacement of the bag [181],

GCR ALEL 1Grade of Recommendation A (Level of Evidence 1)

- propofol – every 6-12 hours [176-179],

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

- parenteral nutrition – every 24 hours, upon manual addition of lipids to the bag – upon bag replacement [176],

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

- lipid emulsion – every 12 hours [176,179].

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Recommendations for catheter use.

Comment:

Catheter function (performance) is the ability to freely aspirate blood from the catheter lumen and infuse into the catheter lumen.

Signs of catheter dysfunction (impaired performance) are signs of occlusion:

• blood return through the catheter is slow, difficult, or completely absent,

• resistance is felt during infusion (flushing) or infusion (flushing) is impossible (frequent high-pressure alarms appear when using an infusion pump),

• swelling or infusion leakage appears at the insertion site.

  In case of impaired catheter performance, it is recommended to follow the catheter management and occlusion resolution algorithm according to internal regulations [176-180].

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

• It is recommended to use the following thrombolytics/fibrinolytics to restore CVC performance in case of thrombotic occlusion [176-180]:

• tissue plasminogen activator (alteplase) - 1 mg/ml, max. dose 4 mg,

GGR BLEL 3Grade of Recommendation B (Level of Evidence 3)

- Urokinase 5000 IU/ml,

GGR BLEL 3Grade of Recommendation B (Level of Evidence 3)

- products based on taurolidine with urokinase 5000 IU/ml,

GGR BLEL 3Grade of Recommendation B (Level of Evidence 3)

- reteplase, tenecteplase, alfimeprase.

Level of Evidence CGrade of Recommendation 2Level of Evidence C (Grade of Recommendation 2)

• In children weighing less than 30 kg, it is recommended to administer the thrombolytic/fibrinolytic in a volume of 110% of the internal lumen volume of the catheter [176-180].

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Flushing.

Comment:it is recommended to use single-dose vials/ampoules, single-use large-volume vials, or prefilled sterile syringes.

Comment:

Locking/disconnecting.

Comment:

A needleless connector must not be closed with a cap, as this damages its design.

Comment: it is recommended to administer locking solutions in a volume not exceeding 1 internal lumen volume of the catheter plus the volume of additional devices plus 10% (in pediatrics) / 20% (in adults) of the resulting volume.

Comment:

Indications are the treatment and prevention of CLABSI in patients with long-term CVCs in case of multiple episodes of CLABSI in history, and in patients at high risk of developing CLABSI.

Comment:

Before using locking solutions as indicated, their systemic effect and the compatibility of ethanol with the catheter material must be evaluated.

Comment:

To maintain positive pressure in the catheter, leave a small amount of locking solution in the syringe before disconnecting it, or close the clamp on the catheter while simultaneously injecting the last 0.5 ml of the locking solution. Consider the anti-reflux characteristics of the catheter and needleless connector.

Catheter care recommendations

Securing.

Comment:

Catheter securement prevents complications associated with catheter dislocation and motion, reduces the incidence of phlebitis and thrombosis, and decreases the likelihood of insertion site infection and CLABSI.

In the absence of securement devices, non-sterile roll adhesive tape, matte or transparent (depending on the type of sterile dressing), as well as non-adhesive bandages (tubular, self-fixing elastic bandages) can be used for securement. Bandages provide a low level of securement.

Replacement of securement devices is performed according to the manufacturer's recommendations or during dressing changes.

Comment:

The use of an extension set allows the catheter to be secured, eliminates micro-movements of the catheter, and allows working with the catheter through the extension port (cannula). The use of an extension set reduces the incidence of phlebitis, thrombosis, dislocation, and insertion site infection. The use of integrated PVCs (having a built-in extension set) is recommended.

Dressing change.

Comment:

1) non-adhesive sterile gauze pad,

2) adhesive:

- transparent polyurethane with/without chlorhexidine,

- opaque non-woven fabric.

The choice of dressing depends on: catheter type, likelihood of bleeding and insertion site infection, skin condition, allergy or sensitivity to a particular type of dressing, patient preferences, durability of dressing adhesive properties depending on skin type, and ease of changing. Preference should be given to the dressing associated with the lowest probability of complications, as frequent dressing changes increase the risk of infection.

Comment:

Contraindications to use are sensitivity or allergy to chlorhexidine (2%), skin diseases, and heavy exudation.

• peeling off, including partial edge peeling,

• visual contamination,

• condensation under the dressing,

• discharge/blood in the insertion site area,

• soaking/wetting,

• signs of skin integrity breach under the dressing,

• need for visualization under an opaque dressing (only in case of local tenderness or other signs of local infection; in other cases, use palpation for assessment) [176-179].

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Port Catheter.

Comment:

It is convenient to combine Huber needle replacement with dressing changes.

Catheter Removal.

Comments:

Do not perform routine microbiological testing of removed central and peripheral venous catheters in the absence of suspicion of catheter-related bloodstream infection.

8. Transfusion Support

Comments: Transfusions may not be required for well-compensated patients recovering from induced aplasia. However, in the event of upcoming intensive chemotherapy in the absence of clinical manifestations of anemic syndrome, red blood cell transfusions may be justified. The decision to administer transfusions should be based primarily on clinical rather than laboratory data [184, 185].

Comments: it has been shown that the use of leukoreduced blood components reduces the incidence of febrile non-hemolytic transfusion reactions, and also significantly decreases the likelihood of patient HLA alloimmunization and the transmission of certain transfusion-transmitted infections (cytomegalovirus, Epstein-Barr virus).

• stable neonates with a platelet count drop to ≤25×10⁹/L;

• stable patients with a platelet count drop to ≤10×10⁹/L;

• febrile patients with a platelet count drop to ≤15×10⁹/L;

• patients at high risk of bleeding with a platelet count drop to ≤20×10⁹/L;

• prior to minor surgical procedures in non-critical sites with a platelet count drop to ≤20×10⁹/L;

• prior to lumbar puncture, with a platelet count drop to ≤40×10⁹/L;

• prior to percutaneous liver biopsy, if the platelet count is ≤50×10⁹/L;

• during surgical interventions in critical sites (e.g., central nervous system), if the platelet count is ≤75-100×10⁹/L;

• prior to other surgical interventions with a platelet count of ≤50×10⁹/L

  Grade of recommendation C (Level of evidence 5)

Comments: an increased risk of bleeding is observed in patients receiving anticoagulants, patients with disseminated intravascular coagulation (DIC), sepsis, etc.

• minor hemorrhagic syndrome and a platelet count drop to ≤10×10⁹/L;

• moderate hemorrhagic syndrome and a platelet count drop to ≤20×10⁹/L;

• severe hemorrhagic syndrome and a platelet count drop to ≤30×10⁹/L;

• bleeding in a critically important location (e.g., CNS) and a platelet count drop to ≤100×10⁹/L

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

• neonates: 10–15 mL/kg

• children with a body weight of more than 10 kg: 10 mL/kg

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

• It is recommended to transfuse granulocyte concentrate in children diagnosed with neuroblastoma and prolonged neutropenia (neutrophil count less than 200/µL) in the presence of a severe bacterial or fungal infection refractory to adequate antimicrobial therapy [186].

• Grade of recommendation C (Level of evidence 5)

• It is recommended to transfuse donor blood plasma in patients diagnosed with neuroblastoma in the presence of clinically significant bleeding combined with an elevation of activated partial thromboplastin time (aPTT) and/or international normalized ratio (INR) of more than 1.5 times the upper limit of normal [186].

GCR CLOCE 5Grade of Recommendation C (Level of Evidence 5)

Comments: cryoprecipitate transfusions for acquired fibrinogen deficiency caused by various etiologies are recommended when its serum concentration falls below 1 g/L. Cryoprecipitate transfusions when blood concentration drops below 1.5 g/L are recommended for patients with acute promyelocytic leukemia, severe intraoperative bleeding, and patients with sepsis who develop hemorrhagic syndrome.

9. Diagnosis and Treatment of Venous Thrombosis

Comments.

Currently, there are no specific guidelines on the choice of a particular imaging method in children with suspected thrombosis, depending on age and the location of the suspected thrombosis. When choosing an imaging method, one should be guided by the availability of the method, as well as recommendations adopted for adult patients. Thus, for detecting thrombosis of the upper and lower extremity veins, as well as the axillary, subclavian, and internal jugular veins, it is indicated to use ultrasonic diagnostic methods, for example, Doppler ultrasound (USDG). At the same time, if clinical signs of calf vein thrombosis persist and USDG results are negative, it is recommended to repeat USDG in a week in order to rule out the spread of calf vein thrombosis. If proximal spread of femoral vein thrombosis is suspected, magnetic resonance venography can be used. For the diagnosis of central vein thrombosis, it is recommended to use contrast-enhanced magnetic resonance venography. If this diagnostic method cannot be used, multi-detector computed tomographic venography may be used. For the diagnosis of pulmonary embolism (PE), CT pulmonary angiography is indicated. In the presence of a contraindication to the administration of iodine-containing contrast or X-ray radiation, MR angiography can be used. For the diagnosis of cerebral venous sinus thrombosis (CVST), MRI using T2* and angio modes is indicated. If urgent MRI diagnostics is not possible, contrast-enhanced CT venography can be used. If thrombosis localized in the area of the heart chambers is suspected, echocardiography may be performed.

Comments: asymptomatic (incidental) venous thromboses in children are quite common, especially in cases of prolonged CVC use. The recommendation not to use routine patient screening to detect asymptomatic CVC-associated thrombosis is based on the fact that the detection of such thrombosis may affect the management of the underlying disease and also lead to an unjustified increase in the risk of hemorrhagic complications.

Laboratory diagnostic methods for venous thrombosis in children.

Comments:

Currently, there are no large prospective studies linking changes in coagulological test parameters to the presence of a thrombus. Given that the vast majority of thromboses in children are provoked, changes in indicators such as APTT, PT, fibrinogen, D-dimer concentration, lupus anticoagulant, proteins C, S, antithrombin, coagulation factor activities, as well as changes in global hemostasis assessment methods (thrombodynamics, thromboelastography, thromboelastometry, thrombin generation test) and platelets (platelet aggregation, cytofluorimetry, microscopy) can potentially be a consequence of the course of the underlying disease and/or its complications, rather than thrombosis. The only method that allows detecting venous thrombosis in a child is visualization (ultrasound, USDG, MRI, MR angiography, CT, CT angiography, radiography, angiography), the choice of which will depend on the location of the suspected venous thrombosis.

In case of venous thrombosis detection, it is recommended to perform a coagulological study (coagulogram, antithrombin), a complete (clinical) blood count with platelet count [194, 195, 211, 212].

Detection of underlying antithrombin deficiency or coagulopathy may affect the choice of drug for the prevention and treatment of thrombosis and influence its dosing and the parameters used for monitoring antithrombotic therapy and prophylaxis.

Treatment of venous thrombosis.

Comments.

The choice of therapeutic agent and regimen will depend on the localization, severity of venous insufficiency manifestations, patient's condition, and presence of contraindications to a particular type of therapy. In most cases of non-life-threatening thrombosis, anticoagulant therapy or secondary antithrombotic prophylaxis with low-molecular-weight heparin or unfractionated heparin preparations can be used. Therapy with a low-molecular-weight sodium heparin preparation starts with a starting dose of 100 IU/kg administered subcutaneously every 12 hours. In the first 6 months of life, the starting dose is 150 IU/kg. In some cases, intravenous administration of low-molecular-weight heparin may be used; however, this approach should take into account the shortening of the drug's half-life due to the intravenous route. In cases where there are risks of bleeding or coagulopathy, as well as when stable, controllable pharmacokinetics of the drug is required, it is recommended to use continuous intravenous infusion of unfractionated heparin** monitored by coagulogram parameters and/or anti-Xa activity. Fondaparinux may also be used. If long-term secondary antithrombotic prophylaxis is necessary, oral anticoagulants (warfarin**, rivaroxaban**) can be used in age-appropriate doses. When using warfarin**, INR monitoring is mandatory to maintain target anticoagulation values. In rare situations where developing thrombosis threatens the patient's condition or life, it is necessary to consider thrombolytic therapy (prourokinase**, alteplase**, reteplase / tenecteplase**) or surgical thrombectomy with mandatory supportive therapy, including blood products (FFP, cryoprecipitate), as well as blood coagulation factors (coagulation factors II, VII, IX, X in combination)**, eptacog alfa (activated)**, and anticoagulation system factors (human antithrombin III, human protein C). If resistance to anticoagulant therapy with unfractionated or low-molecular-weight heparin**, as well as fondaparinux, is detected, evaluation of antithrombin activity is indicated, and if decreased, replacement therapy with human antithrombin III concentrate should be administered.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

• All patients with neuroblastoma at all stages of disease therapy, as well as after completion of treatment, are recommended comprehensive rehabilitation, and, if necessary, supportive therapy to improve treatment outcomes and the patient's quality of life, depending on comorbid conditions and complications of primary therapy [55].

GCP CLEL 5Grade of Recommendation – C (Level of Evidence – 5)

Comments: patient rehabilitation should be comprehensive in nature, covering not only medical but also socio-psychological aspects of the patient's adaptation to normal life. Such rehabilitation requires, in addition to medical care, the mandatory participation of psychologists. Rehabilitation programs are developed individually depending on the identified complications of drug treatment, comorbid conditions, and social and psychological problems. Rehabilitation for complications of the disease and treatment is carried out within the framework of the respective nosologies. The pediatric oncologist at the patient's place of residence follows the recommendations provided by the specialists of the treatment facility.

The scope, duration, and nature of rehabilitation measures depend on the patient's age at the time of initial diagnosis and the timing of rehabilitation measures, the scope of treatment administered (polychemotherapy, surgery, radiation therapy, high-dose polychemotherapy with autologous HSCT, etc.), comorbid conditions either caused by neuroblastoma (epidural compression, opsoclonus-myoclonus syndrome, etc.) or unrelated to the tumor (congenital heart defect, etc.).

The initiation of rehabilitation measures depends on the stage and risk group, and begins during the stages of primary polychemotherapy and continues after its completion at all stages of follow-up.

Rehabilitation measures are carried out under the supervision of a pediatric oncologist from the medical organization where the patient received all main stages of therapy.

Rehabilitation is divided into medical, psychological, social, etc.

The program involves educators (preschool and school education), social workers, psychologists, and physicians of various specialties (rehabilitologists, neurologists, endocrinologists, cardiologists, orthopedists, etc.).

Rehabilitation is carried out in regional centers based at outpatient clinics and in specialized medical and rehabilitation centers.

Rehabilitation frequency is 2-3 times a year and can be increased depending on the patient's psychosomatic status.

5. Prevention and Dispensary Observation

Follow-up monitoring plan for patients with NB.

Comments:

Prevention of Pneumocystis carinii infection [57]:

a)      #Co-trimoxazole [Sulfamethoxazole+Trimethoprim] at a dose of 150/750 mg/m² /day, which is equivalent to 5 mg/kg/day of trimethoprim 2-3 days a week (Saturday, Sunday or Monday, Wednesday, Friday)

b)      Skin disinfection: daily showering or wiping with an aqueous solution of chlorhexidine**, treatment of macerations and lesions with brilliant green solution**.

c)      Daily disinfection of the patient's living quarters using disinfectant solutions and bactericidal lamps is necessary; in case of agranulocytosis, daily change of bed and body linen is required.

d)      Strict personal hygiene of parents and visitors, as well as handwashing by staff upon entering the ward (box), is mandatory.

Comments: for patients in the surveillance group, 3 months after surgery or completion of polychemotherapy, a control examination is performed, including assessment of tumor marker levels (NSE, ferritin, LDH), ultrasound of the affected area, MSCT/MRI of the affected anatomical area with contrast enhancement, 123I-MIBG scintigraphy (for initially MIBG-positive tumors) or FDG-PET/CT (for initially MIBG-negative tumors or if FDG-PET/CT was performed at diagnosis), or other radioisotope imaging methods (if performed at diagnosis) (Tables 5.1, 5.2). To minimize radiation exposure, MRI was preferred. The subsequent monitoring algorithm differed depending on the presence or absence of residual tumor.

Table 5.1. Comprehensive clinical, laboratory, and instrumental monitoring of patients with neuroblastoma in the surveillance group in the absence of residual tumor after surgery

Note. * – the baseline starting point for the presented dispensary observation schedules is the examination performed 3 months after surgery.

Comments: the frequency and scope of the examination can be adjusted depending on the status of the underlying disease, the appearance of clinical symptoms suspicious for disease relapse/progression, and the appearance of long-term adverse effects of therapy.

Table 5.2. Comprehensive clinical, laboratory, and instrumental monitoring of patients with neuroblastoma in the surveillance group with residual tumor after surgery/chemotherapy.

Note. * – the baseline starting point for the presented dispensary observation schedules is the examination performed 3 months after surgery; ** – more frequent examinations may be performed if there is a residual tumor with intraspinal/intraforaminal extension.

Comments: the frequency and scope of the examination can be adjusted depending on the status of the underlying disease (presence of residual tumor), the appearance of clinical symptoms suspicious for disease relapse/progression, and the appearance of long-term adverse effects of therapy.

Comments: for intermediate-risk patients, tumor marker levels, ultrasound of the affected area, and CT/MRI of the involved anatomical area with contrast enhancement are assessed once every 3 months (Table 5.3). 123I-MIBG scintigraphy / FDG-PET/MSCT / other radioisotope research methods are performed only in patients with persistent pathological radiopharmaceutical uptake once every 6 months until normalization or if disease relapse is suspected.

Table 5.3. Dispensary follow-up of intermediate-risk patients

Note. Here and in Table 12: * – ultrasound is not used for intrathoracic tumors, therefore a chest X-ray must be performed; ** – more frequent MRI is acceptable in the presence of intraspinal/intraforaminal extension of the residual tumor.

Comments: the frequency and scope of the examination may be adjusted depending on the status of the underlying disease (presence of residual tumor and/or metastatic lesions), the appearance of clinical symptoms suspected of disease relapse/progression, and the emergence of long-term adverse effects of therapy.

Comments: in high-risk patients, tumor marker levels, ultrasound of the affected area, and contrast-enhanced MSCT/MRI of the involved anatomical region (Table 17), as well as contrast-enhanced brain MRI, are assessed once every 3 months. Scintigraphy with ¹²³I-MIBG, PET/CT with FDG/other radioisotope studies are performed only in patients with persistent pathological radiopharmaceutical uptake, once every 6 months until normalization, or if disease recurrence is suspected.

Table 17. Follow-up care for high-risk patients

Comments: the frequency and scope of the examination may be adjusted depending on the status of the underlying disease (presence of residual tumor and/or metastatic lesions), the appearance of clinical symptoms suspected of disease relapse/progression, and the emergence of long-term adverse effects of therapy.

6. Organization of Medical Care

Admission to a 24-hour hospital in the specialty "pediatric oncology/hematology" is carried out according to the following indications:

- in case of suspected NB (initial diagnosis);

- with an established diagnosis of NB to continue staged therapy;

- with an established diagnosis of NB to perform a follow-up examination to assess the status of the underlying disease and evaluate therapy toxicity.

Requirements for the patient's hospital stay and therapy conditions:

A. patient rooms should preferably be equipped with air purifiers or central ventilation.

B. the medical institution providing treatment for patients with malignant tumors, including NB, must include an intensive care unit or ward equipped with all necessary medications and equipment for managing a patient with severe respiratory and cardiovascular failure, septic and other types of shock, hemorrhagic syndrome, renal failure, etc. It must be possible to perform extracorporeal detoxification (hemodialysis) and mechanical ventilation.

C. requirements for the availability of specialists and diagnostic/treatment facilities of related specialties:

A medical organization treating a patient with NB must include an anesthesiology and reanimation unit (ward) and a surgery department capable of performing thoracic and abdominal surgeries of any complexity. In addition, it must employ an endocrinologist, neurologist, ophthalmologist, ENT specialist, and neurosurgeon. Cytological, immunological, bacteriological, biochemical, and emergency laboratories are mandatory.

In the absence of the above conditions or the impossibility of performing certain medical procedures (e.g., neurosurgical intervention in patients with intraspinal extension of NB, etc.), patients must be referred to specialized higher-level medical institutions (federal, national centers).

Indications for emergency hospitalization:

- with an established diagnosis of NB and the presence of life-threatening conditions (LTC);

- with an established diagnosis of NB and suspected relapse/progression of the disease;

- with an established diagnosis of NB and the development of severe organ toxicity during specific therapy.

Indications for discharging a patient from the hospital include:

- completion of all ongoing therapy or one of the treatment stages with a satisfactory somatic status of the patient.

The patient is handed over to the local pediatrician/hematologist/pediatric oncologist after the completion of a stage or the entire treatment protocol. The local pediatrician (hematologist/pediatric oncologist) is guided by the recommendations provided by the specialists of the institution that carried out the main stages of treatment.

Dispanserization (follow-up) records are maintained by the pediatrician, pediatric oncologist/hematologist until the patient is transferred to adult care.

7. Additional Information

1. Stratification of patients into risk groups

Modern treatment of patients with NB is based on differentiated therapeutic approaches in three risk groups – observation (low risk), intermediate risk, and high risk [60]. Within the framework of these NB treatment guidelines, criteria for patient risk stratification developed by the German Childhood Cancer Neuroblastoma Group (protocol NB2004) are used [13]. Within this approach, stratification criteria include age at diagnosis (infants under 1 year of age and children older than 1 year), tumor stage according to the International Neuroblastoma Staging System (INSS), MYCN gene status (presence or absence of amplification), and 1p locus status (presence or absence of aberrations). Depending on the combination of prognostic factors, patients are divided into 3 groups: observation (low risk), intermediate risk, and high risk (Table 4).

Table 4. Risk stratification criteria*

*see comments for patients with stage 1 according to INSS in the presence of MYCN gene amplification and patients with stage 4 according to INSS disease at the age of 12–18 months in the absence of MYCN gene amplification and absence of segmental aberrations by MLPA.

Observation group

The initial volume of therapy for patients stratified into the observation (low-risk) group is determined depending on the extent of the tumor process (localized forms of the disease or metastatic - stage 4S) and the presence of life-threatening symptoms (LTS) at the time of diagnosis. Surgical intervention is considered as the main treatment method, predominantly in patients with localized stages of the disease. In the presence of LTS, chemotherapy according to the N4 regimen (maximum number of courses 4) is indicated [13]. For patients with intraspinal tumor extension, the issue of neurosurgical intervention may be considered.

Intermediate-risk group

All patients stratified into the intermediate-risk group are indicated to receive intensive induction chemotherapy, including 6 alternating courses according to the N5 and N6 regimens (N4 courses are performed in children under 6 months of age); surgical treatment can be performed initially or delayed. After completion of induction therapy, 4 courses of therapy according to the N7 regimen are administered, followed by differentiation therapy (9 courses). External beam radiation therapy to the primary tumor bed is administered to patients in the presence of a metabolically active tumor after the induction therapy stage and depending on the patient's age [13].

High-risk group

All patients stratified into the high-risk group are indicated to receive intensive induction chemotherapy, including 6 alternating courses according to the N5 and N6 regimens (N4 courses are performed in children under 6 months of age) or chemoimmunotherapy (according to indications) and delayed surgical treatment. After completion of induction therapy, high-dose therapy is administered followed by autologous peripheral hematopoietic stem cell transplantation (auto-HSCT). Subsequently, it is recommended to conduct differentiation therapy (9 courses) and 5 courses of immunotherapy with dinutuximab beta. External beam radiation therapy to the primary tumor bed is administered to patients in the presence of a metabolically active tumor after the induction therapy stage [13].

2. Evaluation of treatment response in neuroblastoma patients of all risk groups

To analyze the effectiveness of the therapy, international criteria for evaluating treatment response in neuroblastoma patients [12] are used, modified by the mandatory use of MIBG scintigraphy and/or 18F-FDG PET/CT and/or other radioisotope imaging methods. Within these criteria, the following response options are distinguished: complete response, very good partial response, partial response, mixed response, stable disease, and progression (Table 7.7.1). All diagnostic methods specified in the "Diagnostics" section are used to evaluate the response to therapy.

Table 7.7.1. Criteria for evaluating treatment response in neuroblastoma patients

Response assessment for patients in the observation group is carried out 3 months after surgical treatment or 3 months after the end of chemotherapy (for patients with LTS who underwent chemotherapy).

Response assessment for intermediate-risk patients is carried out after the completion of the induction therapy stage and at the end of the entire treatment plan.

Response assessment for high-risk patients is carried out after 4–6 courses of induction therapy, after intensified induction therapy (if performed), three months after high-dose chemotherapy and auto-HSCT, before starting immunotherapy, at stages of post-consolidation treatment, and at the end of the entire therapy plan.

3. Specifics of radiation therapy in neuroblastoma patients

Guidelines for radiation therapy – see section 3 of these guidelines.

Technical requirements for external beam radiation therapy equipment

Medical linear accelerator with a photon energy of 6 MV – 10 MV, equipped with a multileaf collimator and, highly desirably, image-guided radiation therapy (IGRT) system(s).

Head and body immobilization devices.

X-ray computed tomography scanner for topometry.

3-D radiation treatment planning system.

Pre-radiation preparation

Planning is carried out based on topometry performed on an X-ray computed tomography scanner adapted for radiotherapy needs (CT simulation). Marking is performed using individual immobilization devices: for localization in the head and neck region - thermoplastic masks and a vacuum mattress; for localization in the mediastinal, abdominal, and pelvic regions – a vacuum mattress.

Scanning is performed with a slice thickness of 1–5 mm depending on the localization of the metabolically active residual tumor: in the head and neck region - 1–2 mm, in the mediastinal, abdominal, and pelvic regions – 2–5 mm.

It should be taken into account that simulation and radiation therapy in patients under 5 years of age may require general anesthesia.

Determination of irradiation volumes

Gross tumor volume (GTV) is defined as the metabolically active residual tumor. To refine it, it is preferable to fuse simulation CT scans and MRI images performed for diagnostic purposes prior to treatment planning, as well as SPECT/CT data from MIBG scintigraphy.

Clinical target volume (CTV) includes GTV with a margin of 1–2 cm, depending on the patient's age, localization, and volume of the residual tumor, taking into account anatomical barriers to tumor spread (bones, parenchymal organs).

The planning target volume (PTV) includes the CTV with an additional margin of 3-10 mm in accordance with the internal standards of the clinic and should be:

- for the head and neck – 3-7 mm

- for the mediastinum, retroperitoneum, and pelvis – 5-10 mm

A reduction in PTV margins is acceptable when performing daily image-guided setup verification using cone-beam computed tomography (CBCT) on the linear accelerator couch prior to the treatment session.

Dose and Fractionation

The total tumor dose (TTD) is 36-40 Gy with conventional fractionation (once daily, 5 days a week) at a fractional dose of 1.6-1.8 Gy. If tolerance doses to organs at risk cannot be achieved during treatment planning in this mode, a TTD of 21 Gy at a fractional dose of 1.5 Gy is recommended.

Treatment Planning.

The minimum requirement for treatment planning is 3D conformal radiotherapy.

For most patients, the use of advanced intensity-modulated radiotherapy techniques (IMRT, VMAT) can reduce the volume of tissue receiving a high radiation dose. However, it should be taken into account that this may increase the volume of tissue exposed to low radiation doses.

Planning must account for the maximum permissible radiation doses to surrounding critical organs.

- Kidneys: if possible, Dmean < 15 Gy, V20 < 32%, and for a single remaining kidney, Dmax < 12 Gy, V10 < 25-30%

- Liver: V20 < 50%

- Bones: if the spine is included in the PTV, it should be irradiated symmetrically to prevent scoliosis (the allowable minimum dose to the irradiated vertebra is 80% of the prescribed dose)

- Spinal cord: whenever possible, the dose to the spinal cord should not exceed 30 Gy for a small segment (2-3 vertebrae) or 20 Gy for larger segments, especially in young children.

- For most organs, tolerance doses for children have not been established. Guidance should be sought from QUANTEC recommendations.

Treatment Delivery.

Target localization is verified by performing CBCT or, less preferably, portal imaging to correct for displacements. Verification is typically performed during the first 3-4 treatment sessions to rule out systematic setup error, and thereafter once a week. When PTV margins are reduced or large random displacements are detected during the first days of treatment, daily patient position verification is recommended.

Radiation Reactions and Complications.

Acute radiation toxicities occur during radiotherapy and within the first 90 days after its completion. These effects are specific to the irradiated tissues and are usually well tolerated by patients. However, they can sometimes be quite severe, requiring additional medical management and treatment interruption. Acute effects are largely temporary and do not cause permanent deterioration of tissue and organ function.

Nausea, vomiting, diarrhea, and blood count changes are the most common occurrences. Their severity largely depends on the treatment volume, the location of the residual tumor, and the patient's age. Most of these resolve with appropriate supportive care and leave no lasting health effects for the young patient.

In case of decreased blood counts, replacement transfusion therapy is administered, and colony-stimulating factors are used, the administration of which should be scheduled outside the irradiation period, i.e., at the end of the week and on weekends.

The severity of late radiation reactions depends on the localization, cumulative radiation dose (CRD), and the child's age. Severe long-term consequences are generally rare due to the small volume of irradiated tissues and the use of modern radiotherapy techniques.

The development of skeletal deformations, including spinal deformities, can be avoided with symmetrical irradiation of the vertebral bodies. Spinal cord damage does not occur if permissible radiation doses are observed.

The most serious complications are to be feared from the kidneys when large retroperitoneal tumors are irradiated. Exceeding tolerance doses can cause degeneration and sclerosis of the renal arterioles. As a result, the decreased blood flow leads to the degeneration of renal glomeruli and tubules, and fibrosis of the renal parenchyma. Renal dysfunction causes hypertension, edema, uremia, and can be fatal.

Secondary tumors are considered the most serious consequence of cancer treatment. Both radiation therapy and chemotherapy contribute to their development. They can occur many years after the completion of the programmed treatment. Compared to adult patients, children live much longer after radiotherapy, and the risk of developing secondary tumors is most relevant for them.

4. Specifics of the surgical treatment of neuroblastoma

Surgical treatment of patients with NB across all risk groups has been a subject of scientific discussion for several decades. Surgery is the primary treatment method for patients in the observation group. In patients with localized forms of the observation group, mandatory assessment of risk factors via imaging is necessary to plan the scope of the surgical intervention, while the intervention itself should not be of a mutilating nature.

High-risk NB is more frequently characterized by locally invasive growth with potential involvement of vital structures, including major vessels and parenchymal organs. The subject of discussion is the impact of radical surgical interventions in this cohort of patients on the disease prognosis, given the presence of distant metastases and a high risk of severe surgical complications during attempts at radical tumor removal. In addition, the timing of the surgical intervention and the criteria for assessing the radicality of the intervention have remained debatable. It should be noted that unlike other types of malignancies where radical intervention is understood as proven negative resection margins (microscopically radical removal), in NB microscopic confirmation of the resection margins is not required, and surgical interventions with macroscopically complete removal are classified as radical. The latter includes the removal of the entire tumor mass and regional lymph nodes identified by visual inspection and palpation during surgery by the operating surgeon. It is highly advisable to confirm the completeness of resection by performing postoperative anatomical imaging.

Surgical treatment (including timing) was considered in the context of the overall treatment plan according to risk groups, as it is an integral stage of multimodal therapy for patients with NB.

Minimally invasive access (laparoscopy, thoracoscopy) for neuroblastoma resection is recommended for localized tumor forms (adrenal neuroblastoma, posterior mediastinum) and the absence of IDRF risk factors according to preoperative imaging. In cases of tumor contact with major vessels, minimally invasive access may be considered provided the surgeon and surgical team have experience performing such surgical interventions [27, 28].

Decompressive laparostomy is indicated for patients with neuroblastoma who develop intra-abdominal hypertension due to a large primary tumor size or hepatomegaly in metastatic liver involvement [63-69]. Approaches to the surgical treatment of ACS in patients with NB (predominantly stage 4S):

1. Consider intra-abdominal hypertension in children as a sustained increase in intra-abdominal pressure of 10 mm Hg or more, recorded during three standard measurements at intervals of 4-6 hours.

2. Considering the severity of the patient's condition and the irreversibility of the ACS course against the background of oncological pathology, all patients should be monitored in an intensive care unit. The examination and treatment tactics, as well as the timing of certain procedures, are developed individually in each clinical case, according to the protocol for treating the underlying disease.

3. Measure intra-abdominal pressure in the urinary cavity, preferably using closed systems, to prevent ascending urinary tract infection in immunocompromised patients of an oncohematological inpatient facility. Monitor intra-abdominal pressure as a routine procedure in patients at risk for developing abdominal compartment syndrome.

4. Implement patient management tactics within the framework of interdisciplinary collaboration involving an anesthesiologist-intensivist, oncologist, and surgeon, which is the key to successful therapy when monitoring this group of patients.

5. Consider the development of abdominal compartment syndrome as an absolute indication for decompressive laparostomy due to the irreversibility of the process. Determine the indications for decompressive laparostomy, the need for simultaneous biopsy, the possibility of primary tumor removal, as well as the timing and risks of these surgical interventions within the framework of interdisciplinary collaboration.

6. Any infection-resistant, histologically inert, non-absorbable sheet material—specifically a polymer mesh implant***—may be used as the plastic component for performing decompressive laparostomy. Fixation of the material should also be performed using non-absorbable surgical suture material.

7. If there is no need to enter the abdominal cavity, preserve the integrity of the parietal peritoneum when performing decompression whenever possible, and fix the plastic material to the edges of the myofascial wound directly above it.

8. Closure of the laparotomy wound upon completion of decompression should be performed under the control of intra-abdominal pressure, ventilation parameters, and cardiovascular performance.

9. In the postoperative period, if a subcutaneous hematoma develops after plate placement, evacuation/drainage of the hematoma must be performed to prevent its suppuration.

10. In case of wound suppuration following decompressive laparostomy, revision surgery is required with plate removal, debridement of purulent foci, and excision of the wound edges. If necessary, implantation of a larger plate is acceptable.

11. In the event of necrosis of the separated skin-fat flap area over the plate, conservative wound management "under an eschar" is acceptable, provided there is no development of a purulent process. Conservative management can be carried out until the protocol-specified date for surgical intervention regarding the underlying disease or until the completion of treatment for the underlying disease.

12. If abdominal compartment syndrome progresses after decompressive laparostomy, repeat decompression with the implantation of a larger plate is indicated.

13. Plate removal can be performed simultaneously with tumor resection within the timeframes determined by the treatment protocol. If tumor resection is not necessary, the plastic material may be left in place.

14. If necrosis of the skin-fat flap area was observed during the treatment stages and conservative wound management "under an eschar" was performed, in order to prevent the formation of gross scars of the anterior abdominal wall in the future, even in the absence of indications for tumor removal during or after the completion of treatment for the underlying disease, plate removal with simultaneous anterior abdominal wall plastic surgery using local tissues must be performed.

15. Reconstruction of the anterior abdominal wall after removal of the plastic material should preferably be performed using native tissues, sequentially approximating corresponding layers.

16. Patient follow-up is carried out at the intervals and in the scope determined by the treatment protocol for the underlying disease.

Criteria for Evaluating the Quality of Medical Care

XII. Criteria for evaluating the quality of medical care 

References

Appendix A1. Working Group Composition

1. Clinical oncologists:

Tatiana V. Shamanskaya, MD, DSc, Member of RODOG, Head of the Department of Embryonal Tumors, Institute of Oncology, Radiology and Nuclear Medicine, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Svetlana R. Varfolomeeva, MD, DSc, Prof., President of RODOG, Director of the Research Institute of Pediatric Oncology and Hematology, National Medical Research Center of Oncology named after N.N. Blokhin of the Russian Ministry of Health, Professor of the Department of Pediatric Oncology named after Acad. L.A. Durnov, Russian Medical Academy of Continuous Professional Education of the Russian Ministry of Health, Moscow

Denis Yu. Kachanov, MD, DSc, Member of RODOG, Head of the Department of Clinical Oncology, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health, Deputy Director of the Institute of Oncology, Radiology and Nuclear Medicine, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev

Galina A. Novichkova, MD, DSc, Prof., Member of RODOG, Scientific Director of the National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health, Chief freelance pediatric oncologist-hematologist of the Ministry of Health

Margarita B. Belogurova – MD, DSc, Prof., Member of RODOG, Head of the Department of Oncology, Pediatric Oncology and Radiation Therapy, Saint Petersburg State Pediatric Medical University, Head of the Department of Chemotherapy (Antineoplastic Drug Therapy) and Combined Treatment of Tumors in Children, Saint Petersburg Clinical Scientific and Practical Center for Specialized Types of Medical Care (Oncological) named after N.P. Napalkov of the Russian Ministry of Health

Dinara T. Utalieva, Member of RODOG, Pediatric Oncologist at the Clinical Oncology Department, Research Laboratory Assistant at the Department of Catamnesis of Children after Oncological Diseases, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Nikolay S. Ivanov, Member of RODOG, Pediatric Oncologist at the Clinical Oncology Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Marina V. Rubanskaya, MD, PhD, Member of RODOG, Head of Pediatric Oncology Department No. 1 (Tumor Chemotherapy, Thoracoabdominal Localization), National Medical Research Center of Oncology named after N.N. Blokhin of the Russian Ministry of Health

Larisa G. Fechina, MD, PhD, Member of RODOG, Deputy Chief Physician for Oncology and Hematology, Regional Children's Clinical Hospital, Yekaterinburg

Yulia V. Dinikina, MD, PhD, Member of RODOG, Head of the Department of Chemotherapy for Oncohematological Diseases and Bone Marrow Transplantation for Children, National Medical Research Center named after V.A. Almazov of the Russian Ministry of Health

2. Transplantation Group:

Ilya V. Kazantsev, MD, PhD, Member of RODOG, Head of the Bone Marrow Transplantation Unit for Children No. 2, Gorbacheva Research Institute of Pediatric Oncology, Hematology and Transplantology, Associate Professor of the Department of Hematology, Transfusiology and Transplantology with a Course in Pediatric Oncology named after Prof. B.V. Afanasyev, Pavlov First Saint Petersburg State Medical University

Rimma D. Khismatulina – Member of RODOG, Hematologist at the Hematopoietic Stem Cell Transplantation Department No. 1, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Kirill I. Kirgizov, MD, PhD, Member of RODOG, Deputy Director for Science, Research Institute of Pediatric Oncology and Hematology named after Academician of RAMS L.A. Durnov, Acting Head of Department, Leading Researcher at the Department of Pediatric Bone Marrow and Hematopoietic Stem Cell Transplantation, National Medical Research Center of Oncology named after N.N. Blokhin of the Russian Ministry of Health

3. Critical Care Physicians

Igor G. Khamin, MD, PhD, Member of RODOG, Head of the Intensive Care Unit, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Ivan A. Kryukov, Member of RODOG, Anesthesiologist-Intensivist at the Intensive Care Unit, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

4. Radiation Therapists:

Alexey V. Nechesnyuk, MD, DSc, Member of RODOG, Head of the Radiation Therapy Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Anastasia Yu. Usyshkina, Member of RODOG, Pediatric Oncologist at the Radiation Therapy Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

5. Surgical Group:

Nikolay S. Grachev, MD, DSc, Prof., Member of RODOG, General Director of the National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Dmitry G. Akhaladze, MD, DSc, Member of RODOG, Pediatric Surgeon at the Department of Oncology and Pediatric Surgery, Head of the Thoracoabdominal Group, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Sergey R. Talypov, Member of RODOG, Pediatric Surgeon at the Department of Oncology and Pediatric Surgery, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Sergey S. Ozerov, Member of RODOG, Neurosurgeon, Morozov Children's City Clinical Hospital of the Moscow Healthcare Department

Polad A. Kerimov, Member of RODOG, MD, DSc, Head of Surgical Department No. 2 (Thoracoabdominal and Musculoskeletal Tumors), Research Institute of Pediatric Oncology and Hematology named after Academician of RAMS L.A. Durnov, National Medical Research Center of Oncology named after N.N. Blokhin of the Russian Ministry of Health

6. Imaging Group:

Galina V. Tereshchenko, MD, PhD, Member of RODOG, Head of the Radiology Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

7. PET and Radioisotope Diagnostic Methods:

Yuri N. Likar, MD, DSc, Member of RODOG, Head of the PET and Radionuclide Diagnostics Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

8. Laboratory of Molecular Genetics

Alexander E. Druy, MD, PhD, Member of RODOG, Head of the Molecular Oncology Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Natalia A. Andreeva, MD, PhD, Member of RODOG, Pediatric Oncologist at the Clinical Oncology Department and Researcher at the Laboratory of Molecular Oncology, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

9. Laboratory of Pathological Anatomy

Dmitry M. Konovalov, MD, PhD, Member of RODOG, Head of the Department of Pathological Anatomy, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Vitaly Yu. Roshchin, Member of RODOG, Physician at the Department of Pathological Anatomy, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

10. Nutritional Support Group

Andrey Yu. Vashura, MD, PhD, Nutritionist, Head of the Department of Scientific Foundations of Nutrition and Nutritional-Metabolic Therapy, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Irina V. Korovina, Nutritionist, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

11. Supportive Care Group

Nikolay V. Zhukov, MD, DSc, Head of the Department of Interdisciplinary Oncology, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Dmitry V. Litvinov, MD, DSc, Chief Physician, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Liliya L. Rabaeva, MD, PhD, Pediatric Oncologist at the Older Children's Hematology/Oncology and Neurooncology Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Galina G. Solopova, MD, PhD, Deputy Chief Physician for Infection Control, Head of the Infection Control Department, Hematologist, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Pavel E. Tratchman, MD, DSc, Professor, Head of the Department of Transfusiology, Harvesting and Processing of Hematopoietic Stem Cells, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Anastasia V. Satsuk, MD, PhD, Head of the Department for Continuing Education of Mid-Level Medical Personnel, Epidemiologist, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health, Senior Researcher at the Laboratory for Prevention of Nosocomial Infections, Central Research Institute of Epidemiology of Rospotrebnadzor

Vladislav V. Shchukin, MD, PhD, Head of the Department of Anesthesiology and Intensive Care with Operating Unit, Anesthesiologist-Intensivist, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Olga V. Pimenova, Head Nurse, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Natalia A. Klimova, Senior Nurse of the Pediatric Hematology/Oncology Department, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Yulia L. Shchemelinskaya, Epidemiologist, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health

Sorokina Lyudmila Fedorovna, nurse at the Department of Pediatric Oncology, Head and Neck Surgery, and Neurosurgery, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health.

Zharkov Pavel Aleksandrovich, Doctor of Medical Sciences, Head of the Laboratory of Hemostasis Pathology, National Medical Research Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev of the Russian Ministry of Health.

Conflict of interest: none.

Appendix A2. Methodology for Developing Clinical Guidelines

Target audience of these clinical guidelines:

• pediatric hematologists;

• pediatric oncologists;

• pediatric surgeons;

• radiation therapists;

• pediatricians;

• pediatric intensivists.

Methodology for evidence collection

Methods used for collecting/selecting evidence: searching for publications in specialized peer-reviewed periodicals with an impact factor >0.3.

Search in electronic databases.

The evidence base for the recommendations includes publications from the Cochrane Library, PubMed, and MEDLINE databases.

Methods used for evidence analysis:

• reviews of published studies and meta-analyses;

• systematic reviews with evidence tables.

  Methods used for assessing the quality and strength of evidence:

• expert consensus;

• assessment of the significance of evidence in accordance with the evidence rating scheme (Tables A2.1–A2.3).

  These clinical guidelines provide levels of evidence certainty and recommendation grades in accordance with the guidelines for the development and updating of clinical guidelines (Order of the Russian Ministry of Health No. 103n dated February 28, 2019).

Table A2.1. Scale for assessing the levels of evidence certainty (LEC) for diagnostic methods (diagnostic interventions)

Table A2.2. Scale for assessing the levels of evidence certainty (LEC) for prevention, treatment, and rehabilitation methods (preventive, therapeutic, and rehabilitative interventions)

Table A2.3. Scale for assessing the grades of recommendation (GR) for prevention, diagnostic, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Methodology for validation of guidelines

Validation methods:

• external expert review;

• internal expert review.

Description of the guideline validation methodology

The preliminary version of these recommendations was reviewed by independent experts who were asked to comment on the quality of evidence interpretation and guideline development. An expert review of the presentation of the recommendations and their readability was also carried out.

The recommendations were discussed and approved by leading specialists of specialized federal centers of the Russian Federation and practicing physicians. The draft clinical guidelines was reviewed at meetings of the National Society of Pediatric Hematologists and Oncologists (NSPHO) in 2018 and 2020.

Procedure for updating clinical guidelines.

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

Appendix A3.1. Algorithm for audiological examination in patients with a diagnosed neuroblastoma who are scheduled for chemotherapy including ototoxic drugs (cisplatin**, #carboplatin**) to assess auditory function

Appendix A 3.2. Chemotherapy regimens used for the treatment of neuroblastoma

Regimen N4 [13, 39]

Standard drug dose calculation:

● #Vincristine** 0.75 mg/m² IV bolus, days 1, 3, 5 [13]

● Doxorubicin** 15 mg/m² IV over 30 min, days 1, 3, 5.

● Cyclophosphamide** 300 mg/m² IV over 30 min, days 1–7.

● Supportive therapy:

• Hydration 2000 mL/m², days 1–7;

• mesna** 60 mg/m² × 3 times IV bolus at 0, 4, and 8 hours from the start of cyclophosphamide** infusion, days 1–7;

• antiemetic drugs.

Calculation of drug doses for newborns and infants (children under 12 months of age and children with a body weight < 10 kg):

● #Vincristine** 0.025 mg/kg/day IV bolus, days 1, 3, 5 [13]

● Doxorubicin** 0.5 mg/kg/day IV over 30 min, days 1, 3, and 5.

● Cyclophosphamide** 10 mg/kg /day IV over 30 min, days 1–7.

● Supportive therapy:

• hydration 50 mL/kg /day, days 1–7;

• mesna** 2 mg/kg/day 3 times IV bolus at 0, 4, and 8 hours from the start of cyclophosphamide** infusion, days 1–7;

• antiemetic drugs in age-appropriate dosages.

The interval between courses is 21 days.

Regimen #carboplatin** and etoposide** (for children under 12 months) [94]

Standard drug dose calculation:

• #Carboplatin** 6.6 mg/kg IV as a 1-hour infusion or per os, days 1–3.

● Etoposide** 5 mg/kg IV as a 1-hour infusion or per os, days 1–3.

• Supportive therapy:

• hydration 2000 mL/m², days 1–3;

• antiemetic drugs.

Regimen N5 [13, 39]

Standard drug dose calculation:

● Vincristine** 1.5 mg/m² IV drip over 1 hour, day 1 [72, 73].

● Cisplatin** 40 mg/m² IV drip as a 24-hour infusion, days 1–4.

● Etoposide **100 mg/m² IV drip as a 24-hour infusion, days 1–4.

● Supportive therapy:

• hydration 3000 mL/m², days 1–6;

• #mannitol 40 mL/m² every 6 hours, IV slowly, days 1–5 [13];

• antiemetic drugs.

Calculation of drug doses for newborns and infants (children under 12 months of age and children with a body weight < 10 kg):

● Vincristine** 0.05 mg/kg IV drip over 1 h, day 1 [72, 73].

● Cisplatin** 1.3 mg/kg IV drip as a 24-hour infusion, days 1–4.

● Etoposide** 4.2 mg/kg IV drip as a 24-hour infusion, days 1–4.

● Supportive therapy:

• Hydration 3000 mL/m², days 1–6;

• o #mannitol^** 40 mL/m² every 6 hours, IV slowly, days 1–5 [13];

• antiemetic drugs.

Regimen N5- Q [78]

Standard drug dose calculation:

● Vincristine** 1.5 mg/m² IV drip over 1 hour, day 1 [72, 73].

● Cisplatin** 40 mg/m² IV drip as a 24-hour infusion, days 1–4.

● Etoposide **100 mg/m² IV drip as a 24-hour infusion, days 1–4.

● Supportive therapy:

• Hydration 3000 mL/m², days 1–6;

• #mannitol 40 mL/m² every 6 hours, IV slowly, days 1–5 [13];

• antiemetic drugs.

● Dinutuximab beta at a dose of 10 mg/m2/day

continuously for 5 days, starting from day 5 [78];

Comments: if the drug is intended to be used for the prevention of ototoxicity, the administration regimen of cisplatin** may be modified: the total dose of cisplatin** is divided into 4 infusions lasting 6 hours each (15 minutes after the end of the cisplatin** infusion, a 15-minute infusion of the ototoxicity prevention drug is administered. The next administration of cisplatin** is in 10 hours).

Regimen N6 [13, 39]

Standard drug dose calculation:

●       #Vincristine** 1.5 mg/m² IV drip over 1 h, days 1, 8 [13].

●       #Dacarbazine** 200 mg/m² IV drip as a 1-hour infusion, days 1–5.

●       #Ifosfamide** 1500 mg/m² IV drip as a 20-hour infusion, days 1–5.

●       Doxorubicin** 30 mg/m² IV drip as a 4-hour infusion, days 6, 7.

● Supportive therapy:

• Hydration 3000 mL/m², days 1–8;

• mesna^** 900 mg/m² IV as a 24-hour infusion, days 1–7;

• antiemetic drugs.

Calculation of drug doses for newborns and infants (children under 12 months of age and children with a body weight < 10 kg):

●       #Vincristine** 0.05 mg/kg IV drip over 1 hour, days 1, 8 [13].

●       #Dacarbazine** 6.7 mg/kg IV drip as a 1-hour infusion, days 1–5.

●       #Ifosfamide** 50 mg/kg IV drip as a 20-hour infusion, days 1–5.

●       Doxorubicin** 1 mg/kg IV drip as a 4-hour infusion, days 6, 7.

● Supportive therapy:

• hydration 3000 mL/m², days 1–8;

• mesna^** 30 mg/kg IV as a 24-hour infusion, days 1–7;

• antiemetic drugs.

               Course N6-Q [13,78]

             Standard drug dose calculation:

●       #Vincristine** 1.5 mg/m² IV drip over 1 h, days 1, 8 [13,78].

●       #Dacarbazine** 200 mg/m² IV drip as a 1-hour infusion, days 1–5.

●       #Ifosfamide** 1500 mg/m² IV drip as a 20-hour infusion, days 1–5.

●       Doxorubicin** 30 mg/m² IV drip as a 4-hour infusion, days 6, 7.

● Supportive therapy:

• hydration 3000 mL/m², days 1–8;

• mesna^* 900 mg/m² IV as a 24-hour infusion, days 1–7;

• antiemetic drugs.

●       Dinutuximab beta at a dose of 10 mg/m2/day by continuous infusion for 5 days,

starting from day 6.

Course N7 [13, 39]

Standard drug dose calculation:

●       Cyclophosphamide** 150 mg/m² IV as a 1-hour infusion or per os, days 1–8.

● Supportive therapy:

• mesna** 30 mg/m² × 3 times IV bolus or per os at 0, 4, and 8 h from the start of cyclophosphamide** administration, days 1–8;

• antiemetic drugs.

Calculation of drug doses for newborns and infants (children under 12 months of age and children with a body weight < 10 kg):

●       Cyclophosphamide** 5 mg/kg IV as a 1-hour infusion or per os, days 1–8.

● Supportive therapy:

• mesna** 1 mg/kg × 3 times IV bolus or per os at 0, 4, and 8 h from the start of cyclophosphamide** administration, days 1–8;

• antiemetic drugs.

Drug dose modification [13]

In patients with impaired renal function (hydronephrosis, history of acute renal failure, tubulointerstitial disorders), it is advisable to consider omitting nephrotoxic cytostatic drugs (cisplatin** and #ifosfamide**) and replacing them with equivalent doses of #carboplatin** and cyclophosphamide**.

In course N5, cisplatin** is replaced with #carboplatin** at a dose of 100 mg/m² IV drip as a 24-hour infusion, days 1–4.

Calculation of #carboplatin** doses in neonates and young children (children under 12 months and children with body weight <10 kg): 3.3 mg/kg IV drip as a 24-hour infusion, days 1–4.

In the N6 regimen #ifosfamide** is replaced with cyclophosphamide** at a dose of 375 IV drip over 1 hour, days 1–5.

Calculation of cyclophosphamide** doses in neonates and young children (children under 12 months and children with body weight < 10 kg): 12.5 mg/kg IV drip over 1 hour, days 1–5.

#Irinotecan** and #temozolomide** course [79]

•          #Temozolomide** 150 mg/m2 IV or per os 1 hour before #irinotecan** administration, days 1-5.

•          #Irinotecan** 50 mg/m2 IV drip as a 1-hour infusion, days 1–5.

• Supportive therapy:

• hydration 3000 mL/m2, days 1–8;

• antiemetic drugs.

Comments: When administering #irinotecan**, prophylaxis of irinotecan-associated diarrhea is indicated [95].

#Irinotecan**, #temozolomide**, and #bevacizumab** course [80]

•          #Temozolomide** 100 mg/m² IV or per os 1 hour before #irinotecan administration, days 1-5.

•          #Irinotecan** 50 mg/m² IV drip as a 1-hour infusion, days 1–5.

•          #Bevacizumab** 15 mg/kg IV drip as a 90-minute infusion, days 1–5.

• Supportive therapy:

• hydration 3000 mL/m2, days 1–8;

• antiemetic drugs.

Comments: administration of #bevacizumab** is contraindicated in patients after surgical interventions.

When administering #irinotecan**, prophylaxis of associated diarrhea is indicated [95].

RIST course [81]

•          #Temozolomide** 150 mg/m2 IV drip as a 1-hour infusion, days 8-12.

•          #Irinotecan** 50 mg/m2 IV drip as a 1-hour infusion, days 8–12.

•          #Sirolimus** 3 mg/m2 per os on day 1, 1 mg/m2 per os on days 2-4.

•          #Dasatinib** 2 mg/kg per os on days 2-4

• Supportive therapy:

• hydration 2000 mL/m2, days 8–12;

• antiemetics on days 8-12.

Comments: When administering #irinotecan**, prophylaxis of associated diarrhea is indicated [95].

Course of #topotecan** and #temozolomide**[82]

•          #Topotecan** 0.75 mg/m² IV drip as a 30-60-minute infusion, days 1-5.

•          #Temozolomide** 150 mg/m2 IV drip as a 1-hour infusion, days 1–5.

• Supportive therapy:

• hydration 2000 mL/m2, days 1–5;

• antiemetic drugs.

Course N8 [13]

•          #Topotecan** 1 mg/m² IV drip as a 24-hour infusion (168 hours), day 1

•          Cyclophosphamide** 100 mg/m² IV drip as a 1-hour infusion, days 1–7.

•          Etoposide** 100 mg/m² IV drip as a 1-hour infusion, days 8–10.

• Supportive therapy:

• hydration 2000 mL/m2, days 1–5;

• antiemetic drugs.

Course of #irinotecan** and #temozolomide** and dinutuximab beta (chemoimmunotherapy)[83]

•                           #Temozolomide** 100 mg/m2 IV or per os 1 hour before #irinotecan** administration, days 1-5.

•                           #Irinotecan 50 mg/m² IV drop infusion over 1 hour, days 1–5.

•                           Dinutuximab beta 10 mg/m²/day IV drop infusion over 24 hours, days 1–10.

•                           Supportive care:

• hydration 2000 mL/m², days 1–8;

• antiemetic drugs.

Comments: When administering #irinotecan, prophylaxis of irinotecan-associated diarrhea is indicated

High-dose therapy regimens:

1.         Melphalan + #treosulfan regimen (TreoMel)

[84, 93]:

•              Melphalan 140 mg/m²/course IV drop infusion over 1 hour, day –2;

•              #Treosulfan 42 g/m²/course, 14 g/m²/day IV drop infusion over 2 hours, days –5, –4, –3;

Comments: When used in a tandem high-dose chemotherapy regimen with autologous HSCT, the total course dose of #treosulfan can be reduced to 36 g/m²/course (single dose of 12 g/m²/day)

2.         Melphalan** + #busulfan** regimen (BuMel) [48,51]:

•              Melphalan** 140 mg/m²/course IV drop infusion over 1 hour, day –2;

•              #Busulfan** 16 mg/kg/course, 4 mg/kg/day orally, days –7, –6, –5, –4 [96];

Comments:

- oral #busulfan** is administered 4 times/day, single dose of 1 mg/kg, maintaining a 6-hour time interval between doses

- starting 24 hours before busulfan administration (from day –8) through day –3, anticonvulsant prophylaxis with levetiracetam** at a dose of 20 mg/kg/day in two divided doses is carried out

- when using intravenous forms of busulfan**, the drug is infused over 2 hours at a single dose calculated according to the table below [96]

2. Regimen #carboplatin** + etoposide** + melphalan** (CEM) [48,51]:

•              Melphalan** 180 mg/m²/course, 45 mg/m², IV drop infusion over 30 minutes; days –8, –7, –6, –5;

•              Etoposide 40 mg/kg/course, IV drop infusion over 4 hours, day –4;

•              #Carboplatin** 1500 mg/m²/course, 500 mg/m²/day, IV drop infusion over 1 hour; days –4, –3, –2;

4. Thiotepa + cyclophosphamide** regimen (TC) [85]:

•              Thiotepa 900 mg/m²/course, 300 mg/m²/day, IV drop infusion over 1 hour; days –7, –6, –5;

•              Cyclophosphamide** 6000 mg/m²/course, 1500 mg/m²/day, IV drop infusion over 1 hour; days –5, –4, –3, –2;

Comments: prophylaxis of hemorrhagic cystitis is required: mesna 500 mg/m² 1 hour immediately before the start of cyclophosphamide** infusion, followed by continuous infusion at a dose of 1500 mg/m²/day over 24 hours on days –5, –4, –3, –2, –1;

5. Thiotepa regimen (T) [86]:

Thiotepa 900 mg/m²/course, 300 mg/m²/day, IV drop infusion over 1 hour; days –7, –6, –5;

Comments: when performing high-dose therapy with allogeneic HSCT, the conditioning regimen and graft-versus-host disease prophylaxis are chosen in accordance with the transplant center's internal guidelines.

Dose modifications

Drug dose modifications are made by decision of the transplant center specialists. The decision is made on an individual basis depending on the tolerance of previous chemotherapy courses or the previous high-dose chemotherapy regimen in the case of a second autologous HSCT within a tandem high-dose chemotherapy regimen with autologous HSCT.

Appendix A 3.3. Immunotherapy with dinutuximab beta. Supportive care[87].

Premedication is administered before each infusion:

1. Gabapentin [87].

The patient must receive the first dose of 10 mg/kg/day 3 days prior to the start of dinutuximab beta infusion.

Day 1 - 10 mg/kg/day once daily orally.

Day 2 - 20 mg/kg/day in 2 divided doses orally.

Day 3 - 30 mg/kg/day in 3 divided doses orally.

The maximum single dose of gabapentin is 300 mg.

The daily dose of gabapentin is increased to 2 × 10 mg/kg/day orally on the next day and to 3 × 10 mg/kg/day orally on the day before the start of dinutuximab beta infusion and thereafter.

Oral gabapentin should be tapered off after the intravenous antibody infusion is completed (and started three days before the next immunotherapy cycle); it is possible to continue gabapentin throughout all 5 immunotherapy cycles, in which case gabapentin should be discontinued on the last day of the final dinutuximab beta administration.

2. Opioids [87].

Due to severe visceral and neuropathic pain, opioids are the standard pain management during dinutuximab beta infusion.

Adverse effects of opioid administration include respiratory depression, nausea, vomiting, constipation, pruritus, urinary retention, and lowered seizure threshold.

The safety and efficacy of continuous intravenous opioid administration for pain management are well established for all age groups.

The risk of dependency is classified as low.

Opioid therapy is standard supportive care during dinutuximab beta administration.

The first day of infusion and the first treatment course generally require higher doses of morphine than subsequent days and courses.

●       Morphine** administration starts 2 hours before the start of dinutuximab beta infusion at a dose of 0.02–0.05 mg/kg/h.

●       Thereafter, simultaneously with the dinutuximab beta infusion, morphine** administration is recommended at a rate of 0.03 mg/kg/h. If necessary, an additional bolus dose of 0.02 mg/kg/dose can be given.

●       During continuous infusion of dinutuximab beta, depending on the patient's pain perception, some patients may discontinue morphine** within 3–5 days by progressively decreasing its infusion rate (e.g., to 0.02 mg/kg/h, 0.01 mg/kg/h, 0.005 mg/kg/h).

●       If continuous morphine** infusion is required for more than 5 days, a gradual reduction of the infusion rate by 20% per day is necessary.

●       Subsequent immunotherapy cycles should be initiated with intravenous morphine, including a loading dose, until a safe and well-tolerated pain management regimen is established for the individual patient. If well tolerated and in the absence of pain, cycles 3–5 of immunotherapy can be administered without morphine**.

For moderate neuropathic pain, oral tramadol** may be used.

Other analgesics that may be used:

Nonsteroidal anti-inflammatory drugs (NSAIDs) [87].

- paracetamol**. Analgesic activity is lower than that of NSAIDs. When used, low analgesic activity and a narrow therapeutic window must be taken into account. Recommended dosages: according to national guidelines

Paracetamol: 10–15 mg/kg every 4 to 6 hours either orally (maximum 90 mg/kg/24 hours) or intravenously (maximum 60 mg/kg/24 hours).

- ibuprofen**. Has a longer duration of action (8 hours).

- metamizole sodium. Due to its spasmolytic properties, metamizole sodium is particularly suitable for relieving visceral pain or spastic pain. More useful than repeated short infusions is a continuous infusion at a dose of 2.5–3.0 mg/kg/h, always with careful monitoring of blood pressure values. Recommended dosages: Metamizole sodium 10 mg/kg every 6 hours or continuous infusion at a dose of 2.5–3.0 mg/kg/h.

3. Antihistamine premedication [87].

(e.g., #diphenhydramine**) should be administered as an intravenous injection approximately 20 minutes before the start of each dinutuximab beta infusion. It is recommended to repeat the administration of antihistamines every 4–6 hours as needed during the dinutuximab beta infusion.

Patients should be carefully monitored for anaphylactic and allergic reactions, especially during the first and second courses of therapy.

#Diphenhydramine** — 0.5–1.0 mg/kg IV or orally before starting treatment and then every 4 hours.

Cetirizine (10 mg tabl.) 5 mg once daily (children <30 kg) and 5 mg twice daily (children >30 kg).

Dimetindene 0.1 mg/kg IV.

Other supportive care [87]:

To prevent and manage potential side effects of non-selective NSAIDs acting as type I and II cyclooxygenase (COX) inhibitors and their effect on platelet aggregation (increased risk of hemorrhagic complications, gastrointestinal mucosal damage), proton pump inhibitors (PPIs) or H2-receptor antagonists are indicated in accordance with national guidelines.

For example, Omeprazole 1 mg/kg/day PO or IV.

To manage nausea and vomiting induced by morphine:

- #ondansetron** — 5 mg/m² per day PO or IV

The following medications must be available in the patient's room during treatment:

1. Oxygen supply (mask)

2. Intravenous antihistamines, adrenaline**, and prednisolone** for intravenous administration must be immediately available at the bedside for the management of life-threatening allergic reactions. It is recommended to administer medications for the treatment of allergic/anaphylactic reactions, including prednisolone**, as an intravenous bolus; adrenaline** is administered as an IV bolus every 3–5 minutes as needed, depending on the clinical response. For bronchial and/or pulmonary hypersensitivity reactions, adrenaline** inhalation is recommended and should be repeated every 2 hours depending on the clinical response.

Monitoring of the patient during dinutuximab beta infusion

● Pulse oximetry 24 hours on all days of infusion

● Blood pressure (BP) monitoring: every 10 minutes for the first 30 minutes of infusion, then every 30 minutes.

Indications for discontinuation of dinutuximab beta therapy.

Dinutuximab beta therapy should be permanently discontinued if the following toxicities develop:

At the same time, patients should continue to receive differentiation therapy with #isotretinoin (if a decision on its administration has been made).

• Allergic reactions — grade 3 bronchospasm and grade 4 anaphylactic reactions.

• Grade 3 serum sickness.

• Refractory grade 4 neuropathic pain not responding to IV narcotic agents and other medications, including lidocaine infusions.

• Neurotoxicity: 1) grade 3 sensory changes interfering with daily activities for more than 2 weeks after completion of the dinutuximab beta infusion; 2) objective motor impairments; 3) grade 3 ophthalmological toxicity (i.e., subtotal vision loss on the toxicity scale).

• Grade 4 hyponatremia (<120 mEq/L) despite adequate correction with intravenous fluids; symptomatic hyponatremia persisting for more than 48 hours with a serum sodium level of less than 125 mmol/L.

• Capillary leak syndrome that recurs (grade 3) or reaches grade 4 (requiring ventilatory support).

• Grade 4 skin toxicity.

• Hypotension — grade 4 hypotension not responding to supportive therapy and/or requiring mechanical ventilation; repeated episodes of grade 3 hypotension not responding to crystalloid boluses.

• Grade 3 or higher cardiotoxicity.

Dinutuximab beta dose modification based on adverse event manifestations

General symptoms and fever

Fever >38ºC should be managed with age-appropriate doses of paracetamol and NSAIDs. Persistent fever >38ºC can be managed with physical cooling methods and ibuprofen (if platelet count is adequate). Other antipyretics may be used, except for steroids. Fever is not a reason to modify the dinutuximab beta dose unless the temperature exceeds 40ºC and persists for more than 6 hours despite antipyretic therapy. In this case, the drug infusion is interrupted.

If the patient develops grade 4 constitutional symptoms or fever despite adequate supportive care, but the symptoms resolve to grade 1, dinutuximab beta infusion may be resumed at 50% of the previous dose for the remainder of the therapy.

Grade 3 fever does not require dinutuximab beta dose adjustment, provided there is close dynamic monitoring and the consent of the patient's parents.

Hypotension:

In the event of grade 3–4 hypotension not responding to the administration of 20 mL/kg of 0.9% sodium chloride solution, the following dose modifications are performed:

Dinutuximab beta dose changes during the current course of immunotherapy:

• Stop the dinutuximab beta infusion. Maintain blood pressure using IV fluids and vasopressors if necessary.

• If hypotension resolves to grade 1 with fluid boluses, the antibody infusion can be resumed at 50% speed after 1 hour in order to complete the administration of the total prescribed dose of dinutuximab beta.

• If grade 3 hypotension recurs upon antibody administration, dinutuximab beta infusion must be discontinued, and the patient is subsequently excluded from this protocol.

Instructions for dinutuximab beta dose modification for subsequent courses:

• If the patient tolerates 50% of the dinutuximab beta dose, subsequent courses of dinutuximab beta should be started at the 50% dose. If this dose is well tolerated, the dose can be increased to full in subsequent courses.

• If hypotension is refractory to ongoing therapy and/or the patient requires mechanical ventilation, immunotherapy must be completely discontinued.

Neurotoxicity

If grade 3 or higher neurotoxicity develops (except for confusion), immunotherapy must be discontinued.

Consciousness disturbances

Consciousness disturbances that are clearly not related to fever and supportive medications (diphenhydramine**, morphine**, etc.) require interruption of therapy. Consciousness disturbances associated with temperature spikes require aggressive antipyretic therapy and physical cooling methods. Persistent altered consciousness (>6 hours) due to any cause requires discontinuation of therapy with subsequent re-administration of dinutuximab beta at a 50% dose if this toxicity reverses before the next scheduled dose of the drug.

Neuropathy

There are a small number of reports of peripheral neuropathy associated with antibody administration. Patients experiencing any prolonged motor weakness associated with dinutuximab beta administration must completely discontinue immunotherapy, be excluded from this protocol, and continue differentiation therapy with 13-cis-retinoic acid.

Hyponatremia associated with dinutuximab beta administration.

Patients with symptomatic hyponatremia, persistent (>48 h) decrease in serum sodium below 125 mmol/L, or severe asymptomatic hyponatremia (sodium less than 120 mmol/L) must discontinue the dinutuximab beta infusion. Such patients should not receive further immunotherapy.

An electrolyte imbalance corresponding to grade 3 toxicity on the international scale (especially hyponatremia <124 mmol/L in the absence of symptoms and CNS complications) that normalizes within 24 hours with correction does NOT require dinutuximab beta dose modification, provided this toxicity is considered tolerable by the attending clinician and the patient's parents.

General condition of the patient

Dinutuximab beta treatment is interrupted in case of grade 4 deterioration of the patient's general condition (<20). If the general condition improves to >20, antibody therapy may be resumed at 50% of the dose at which the toxicity was registered.

Grade 3 impairment of the general condition (30–<50) does NOT require drug dose modification, provided this toxicity is considered tolerable by the attending clinician and the patient's parents.

Pain syndrome

Patients experiencing pain during dinutuximab beta administration despite pain prophylaxis (as specified above) should receive additional morphine or other analgesics as needed. Pain severity should be assessed according to international toxicity criteria and using the patient's self-assessment methods.

Hematologic toxicity

All patients should receive transfusion therapy to maintain adequate hemoglobin levels and platelet counts. If a patient develops neutropenia during dinutuximab beta administration, treatment is not discontinued. However, if neutropenia has not resolved by the start of the next treatment course, the next course should be delayed for up to two weeks or until the neutrophil count rises to 1 × 10⁹/L. The dose of dinutuximab beta in subsequent courses should be reduced by 50%.

Grade 4 hematological toxicity that improves to at least grade 2 or baseline levels prior to therapy within one week after treatment completion does NOT require a dose modification of dinutuximab beta, provided that this toxicity is considered tolerable by the responsible clinician and the patient's parents.

Hepatic toxicity.

Alkaline phosphatase: in case of elevated alkaline phosphatase (ALP) levels, the dinutuximab beta infusion should not be interrupted and doses should not be modified, since elevated ALP levels are observed quite frequently and subsequently decrease spontaneously. Therefore, elevated ALP is not a manifestation of hepatic toxicity.

All other manifestations of hepatic toxicity, except for bilirubin levels, should be managed similarly.

Bilirubin: If bilirubin levels are elevated to more than 3 times the upper limit of normal for age, immunotherapy is interrupted until bilirubin levels normalize. After normalization of bilirubin levels, antibody therapy is resumed at a 100% dose.

Nephrotoxicity

Adequate renal function is a prerequisite for immunotherapy. If renal impairment up to grade 3 is observed, it is recommended to avoid nephrotoxic drugs (e.g., indomethacin, etc.).

Cardiotoxicity

Any signs of cardiac pathology will require immediate ECG. If signs of ischemia are present, immediate discontinuation of therapy is indicated. Patients with signs of asymptomatic atrial arrhythmias associated with fever, but without signs of myocardial ischemia or clinically significant hypotension, will be monitored but may continue therapy. Patients with grade 3 cardiotoxic effects require discontinuation of immunotherapy and are excluded from this protocol.

Cardiovascular changes associated with fluid overload may occur. Patients with clinical problems related to fluid overload should receive furosemide** provided that their systolic blood pressure decreases by no more than 40 mm Hg from baseline.

Dinutuximab beta administration must be stopped in case of a persistent drop in systolic blood pressure below 80 mm Hg, which has decreased by at least 20 mm Hg from baseline and has not recovered after a bolus administration of crystalloid solutions or albumin solution (e.g., 20 ml/kg of 0.9% sodium chloride). Intravenous vasopressors may be used if clinically indicated. Treatment can be resumed at 50% of the dinutuximab beta dose after blood pressure has risen to 80 mm Hg.

Dyspnea

Patients who develop dyspnea and oxygen saturation dropping below 90% should receive short-term oxygen supplementation.

If blood oxygen saturation does not rise above 90% without oxygen supplementation, antibody infusion should be discontinued. Infusion may be resumed at a 50% dose once toxicity resolves.

Nausea, vomiting, and diarrhea

Grade 3 nausea, vomiting, and diarrhea do NOT require antibody dose modification, provided that the specified toxicity is considered tolerable by the responsible clinician and the patient's parents.

Skin toxicity

Grade 3 skin toxicity that remains stable or improves with ongoing therapy (e.g., IV diphenhydramine**) within 24 hours does NOT require antibody dose modification, provided that the specified toxicity is considered tolerable by the responsible clinician and the patient's parents.

For patients with grade 4 skin toxicity, immunotherapy is discontinued and patients are excluded from this protocol. However, #isotretinoin therapy should be continued.

Visual impairment

Impairment of visual accommodation correctable with glasses does not require modification of the dinutuximab beta dose, provided that the specified toxicity is considered tolerable by the responsible clinician and the patient's parents.

Grade 3 ophthalmic toxicity (i.e., subtotal vision loss on the toxicity scale) requires discontinuation of antibody infusion. However, #isotretinoin therapy should be continued.

Comments: before starting the course of immunotherapy and after its completion, the patient must be examined by an ophthalmologist.

Taste alterations

Taste alteration does not require antibody dose modification, provided that this toxicity is considered acceptable by the responsible clinician and the patient's parents.

Hypersensitivity reactions:

• Pruritus and urticaria.

Pruritus and urticaria require therapy with antihistamines (e.g., diphenhydramine**). Given the potential for anaphylactic reactions, preventive measures are necessary, including rapid access to adrenaline** and glucocorticoids. In addition, the patient must always have an additional free IV access.

• Moderate symptoms (e.g., localized skin reactions): reduce the infusion rate of dinutuximab beta to 50% and restore the infusion rate after symptom relief. It is necessary to stay at the bedside and monitor the condition. The drug infusion may be fully completed at the initially calculated dose. Antihistamines (diphenhydramine** or chlorphenamine) can be administered every 4–6 hours at the discretion of the attending physician.

• In the presence of moderate symptoms (e.g., hypotension): interrupt antibody infusion, provide supportive symptomatic therapy, stay at the bedside until symptoms resolve. At the discretion of the attending physician, the infusion can be resumed at 50% of the initial infusion rate.

  Upon the appearance of any severe symptoms (any reaction such as bronchospasm, angioedema, or anaphylactic shock): immediate cessation of antibody infusion. Administration of adrenaline**, antihistamines (diphenhydramine** or chlorphenamine), corticosteroids, bronchodilators, or other medical interventions as needed. Patients must be monitored in the hospital for at least 24 hours and until symptoms resolve. If the course of dinutuximab beta administration was stopped, the next course of #isotretinoin must be initiated.

It is necessary to closely monitor for the development of anaphylaxis and allergic reactions, especially during courses 1 and 2 of immunotherapy. In the event of grade 4 anaphylaxis or allergic reactions, patients must discontinue immunotherapy. However, #isotretinoin therapy should be continued.

Grade 3 serum sickness is an indication for discontinuing immunotherapy. However, #isotretinoin therapy should be continued.

Capillary leak syndrome

Instructions for dose modification during a course of immunotherapy in case of clinical development of grade 3 capillary leak syndrome:

• Discontinue antibody infusion.

• If the capillary leak syndrome resolves or the clinical picture improves to grade 1 with supportive care, the dinutuximab beta infusion can be resumed at 50% speed after 1 hour to complete the administration of the prescribed dose.

• If the clinical presentation of grade 3 capillary leak syndrome recurs with continued administration of dinutuximab beta, immunotherapy must be discontinued.

• Persisting grade 3 capillary leak syndrome for less than 7 days is not considered a specific dose-limiting toxicity.

• If grade 4 clinical symptoms require mechanical ventilation, patients discontinue immunotherapy. However, #isotretinoin therapy should be continued.

Instructions for dose modification for subsequent courses:

• If the patient tolerated a 50% infusion of dinutuximab beta, it is possible to consider increasing the drug dose to 100% in the next course.

• If capillary leak syndrome is not resolved with supportive care or requires respiratory support, the patient must discontinue immunotherapy.

Pulmonary toxicity

If grade 3 pulmonary toxicity develops as a component of capillary leak syndrome, the same dose modification recommendations as for grade 3 capillary leak syndrome should be followed.

Infectious status

The development of a grade 3 infection during dinutuximab beta infusion is an indication to discontinue the course of immunotherapy. Missed doses will not be administered additionally at a later date. The next scheduled course of immunotherapy may only be initiated when the infection has completely resolved or is controlled (absence of clinical symptoms and negative blood cultures).

Expected toxicity events that do not require dinutuximab beta dose modification.

The following expected toxicity events do NOT require dinutuximab beta dose modification, provided that there is dynamic monitoring and these toxicity events are considered acceptable by the attending clinician.

• Pain of grade 4 (managed by IV administration of opioid analgesics).

• Fever of grade 3.

• Nausea and vomiting, diarrhea of grade 3.

• Skin toxicity of grade 3 that remains stable and tolerable, or improves with treatment (e.g., IV diphenhydramine**) within 24 hours.

• Electrolyte imbalance of grade 3 (especially hyponatremia <124 mEq/L in the absence of CNS symptoms and complications) that improves with treatment within 24 hours.

• Hepatic toxicity of grade 3 that returns to grade 1 prior to the start of the next course of dinutuximab beta treatment.

• Neurotoxicity of grade 3 with subjective clinical manifestations (e.g., tingling, hot or cold hands, etc.).

• Hematological toxicity of grade 4 that improves to at least grade 2 or baseline levels after the completion of the immunotherapy course.

• Grade 3 (30 - <50%)

• Decreased visual acuity correctable with glasses.

• Dysgeusia.

Non-recommended adjunctive therapies during dinutuximab beta administration.

The following procedures are not permitted.

• Glucocorticoids or other drugs with known immunosuppressive activity must not be used concurrently and for two weeks prior to the initiation of dinutuximab beta therapy, except for life-threatening symptoms.

• The use of intravenous immunoglobulins is strongly discouraged, as immunoglobulins may interfere with antibody-dependent cell-mediated cytotoxicity (ADCC) of dinutuximab beta. Intravenous immunoglobulin should not be administered within 2 weeks after the start and 1 week after the completion of dinutuximab beta therapy.

• It is not recommended to prescribe G-CSF prior to courses of dinutuximab beta immunotherapy.

• Radiation therapy is not recommended (the interval between the completion of radiation therapy and the start of the dinutuximab beta immunotherapy course must be at least 2–3 weeks).

• Chemotherapy or other types of experimental antitumor therapy, except as described in these guidelines, should not be administered.

Appendix A 3.4. Prevention and treatment of chemotherapy-induced nausea and vomiting

All patients under 18 years of age with neuroblastoma undergoing treatment are recommended to have the emetogenic level of medicinal products assessed, and to receive treatment and prevention of chemotherapy-induced nausea and vomiting (CINV) using medicinal products [1].

A.3.4.1. Determination of emetogenicity level and CINV prevention regimen

To select an adequate CINV prevention regimen, the first step is to determine the emetogenicity level (risk of CINV) of the planned antitumor therapy regimen. The emetogenicity level influences the choice of CINV prophylactic agents, their dosages, and duration of use [97]. Appendix A 3.2.6 (Table 1) presents the general classification of emetogenicity for chemotherapy agents according to ASCO (American Society of Clinical Oncology) [98] and COG (Children's Oncology Group) [97] recommendations.

A.3.4.2. Prevention of nausea and vomiting during highly emetogenic chemotherapy

For optimal prevention of acute CINV occurring on the day(s) of chemotherapy administration, children aged 5 years and older and/or weighing 15 kg or more should use a four-drug regimen including a 5-HT3 serotonin receptor blocker, an NK₁ receptor antagonist (ATC classification A04AD: Other antiemetics), #dexamethasone**, and #olanzapine** [99, 10, 101]. Regimens and dosages are presented in Appendix A 3.2.7 (Table 2).

If the antitumor therapy regimen includes a glucocorticoid at a dose equal to or exceeding the dose indicated for antiemetic use, additional administration of a glucocorticoid (to the antitumor therapy regimen) for CINV prophylaxis on that day is not required. The use of #olanzapine** in children under 5 years of age and/or weighing less than 15 kg has not been studied and cannot be recommended.

For optimal prevention of delayed CINV administered within 3 days following the completion of chemotherapy, a combination of #dexamethasone** and #olanzapine** should be used [100, 103]. Regimens and dosages are presented in Appendix A 3.2.7 (Table 2).

If it is not possible to prescribe an NK₁ receptor antagonist (ATC classification A04AD: Other antiemetics), a combination consisting of any 5-HT3 serotonin receptor blocker, #dexamethasone**, and #olanzapine** should be used [99, 100, 102]. Regimens and dosages are presented in Appendix A 3.2.7 (Table 2).

If it is not possible to prescribe #dexamethasone**, palonosetron** should be used as the preferred 5-HT₃ serotonin receptor blocker in combination with an NK₁ receptor antagonist (ATC classification A04AD: Other antiemetics) (if administration is possible) and #olanzapine** [97, 104]. Regimens and dosages are presented in Appendix A 3.2.7 (Table 2).

A.3.4.3. Prevention of nausea and vomiting during moderately emetogenic chemotherapy

For optimal prevention of acute CINV occurring on the day(s) of chemotherapy administration, a two-drug regimen including a 5-HT3 serotonin receptor blocker and #dexamethasone** should be used [97, 105]. Regimens and dosages are presented in Appendix A 3.2.7 (Table 2).

If the antitumor therapy regimen includes a glucocorticoid at a dose equal to or exceeding the dose indicated for antiemetic use, additional administration of a glucocorticoid (to the antitumor therapy regimen) for CINV prophylaxis on that day is not required.

For optimal prevention of delayed CINV administered within 1 day following the completion of cytostatic agents (ATC classification L: Antineoplastic and immunomodulating agents), #dexamethasone** should be used [97, 105]. Regimens and dosages are presented in Appendix A 3.2.6 (Table 1).

If it is not possible to prescribe #dexamethasone**, a combination consisting of any 5-HT3 serotonin receptor blocker and an NK₁ receptor antagonist (ATC classification A04AD: Other antiemetics) should be used [97, 105]. Regimens and dosages are presented in Appendix A 3.2.7 (Table 2).

If it is not possible to prescribe either #dexamethasone** or NK₁ receptor antagonists (ATC classification A04AD: Other antiemetics), palonosetron should be used as the preferred 5-HT3 serotonin receptor blocker [97, 105]. Regimens and dosages are presented in Appendix A 3.2.7 (Table 2).

A.3.4.4. Prevention of nausea and vomiting during low- and minimal-emetogenicity chemotherapy

CINV prevention for low- and minimal-emetogenicity chemotherapy involves single-agent prophylaxis using a 5-HT3 serotonin receptor blocker for low-emetogenicity therapy, or no prophylaxis at all in the case of chemotherapy with minimal emetogenic activity [97].

Regimens and dosages are presented in Table 2.

A.3.4.5. Treatment of breakthrough and refractory emesis

For patients with breakthrough and refractory emesis during cytostatic therapy, it is recommended:

1. If breakthrough CINV occurs during cytostatic therapy (and consequently prophylaxis) classified as minimal, low, or moderate emetogenicity, drugs designated for the next, higher level of prophylaxis must be used.

2. If the patient is already receiving prophylaxis intended for highly emetogenic therapy, the addition of #olanzapine** should be considered in the event of breakthrough CINV (if it was not used previously due to inappropriate age or body weight). If #olanzapine** cannot be used, metoclopramide may be administered as an alternative.

3. If the patient has refractory CINV and is not yet receiving the maximum level of prophylaxis, escalation of antiemetic therapy should be performed. If refractory CINV occurs despite the maximum level of prophylaxis, it is possible to switch the serotonin 5HT3 receptor antagonist being used to palonosetron, or to administer additional doses of serotonin 5HT3 receptor antagonists. If these approaches to prophylaxis fail, it is recommended to add #olanzapine**, metoclopramide**, or other drugs that have shown efficacy in treating breakthrough vomiting in the patient, on an ongoing basis [105, 106].

Table 1 - Emetogenicity levels of antineoplastic agents [97]

Table 2. Doses and regimens of antiemetic drugs [87-95]

Appendix A 3.5. Nutritional Screening and Monitoring (Assessment of Nutritional Status)

Table A4.1. Interpretation of nutritional status based on Z-scores according to WHO reference data [1].

Notes: nutritional status in pediatric oncology is assessed using combined data (clinical, laboratory, instrumental), taking into nutritional risk; anthropometric indicators provide a guideline for determining nutritional status and cannot be the sole determining factor [7]; *– the indicator with the minimum SDS is used in determining nutritional status; SDS – standard deviation score; obesity – simple; hypothalamic; in neuroendocrine diseases; iatrogenic; monogenic; syndromic

Table A.4.2. High-risk factors for nutritional status disorders [7].

Table A.4.3. Main screening tools for identifying the risk of nutritional disorders in pediatrics [7, 19]

Table A.4.4. Recommended daily nutrient and energy requirements for children (per kg of body weight per day) for diet therapy and enteral nutrition calculations [18]

Notes: Requirements are provided as a guideline for calculating and prescribing enteral nutrition; they do not cancel or replace a patient-centered approach to nutritional support prescribing: in each specific case, the clinical picture, possible metabolic and organ dysfunctions should be taken into account, and nutrient intake should be adjusted considering the child's capabilities and tolerance.

Appendix A 3.6. Venous access.

 Indications for removal of an established CVC [182].

1. lack of need for vascular access,

2. presence of complications from the established CVC:

• local and/or systemic signs of infection* (see CVC Removal/Retention in Case of Infection),

• occlusion not responding to treatment measures and agents,

• radiologically confirmed pinch-off syndrome,

• catheter damage (if repair/over-the-wire exchange is not feasible),

• catheter migration when repositioning is not possible,

• mechanical/infectious phlebitis,

• extravasation/infiltration, *

• deep vein thrombosis, **

  3.       catheter placed without maintaining aseptic technique (in emergency settings) – must be removed within 48 hours. Label catheters placed without maintaining aseptic technique.

  * Not mandatory indications for catheter removal; the decision on removal is made individually depending on the need and functioning of the venous access, the possibility of placing a new catheter, and the feasibility of treating the complication.

  ** Not an indication for catheter removal if the catheter tip is correctly positioned, the catheter is functioning, and there are no signs of infection. The catheter can be used for systemic treatment of thrombosis (see Catheter-Associated Deep Vein Thrombosis). Vein thrombosis upon removal of a peripheral venous catheter or PICC carries no risk of pulmonary embolism.

CVC Removal/Retention in Case of Infection [182].

In the presence of local and/or systemic signs of inflammation, the risks and benefits of removing the catheter versus retaining it and providing treatment must be evaluated.

The evaluation is based on:

•       catheter type (long-term or short-term),

•       type of microorganism,

•       feasibility of placing a new catheter,

•       need for venous access.

According to the National Healthcare Safety Network (NHSN)/Patient Safety Component Manual, Chapter 4. Bloodstream Infection Event (Central Line-Associated Bloodstream Infection and Non-central Line Associated Bloodstream Infection), 2024, the following criteria exist for retaining and removing a CVC in case of infection [182].

Attempts to retain and treat the catheter should be made in cases of:

1.       secondary bloodstream infection associated with another focus of infection,

2.       fever alone with negative blood cultures,

3.       laboratory-confirmed catheter-related bloodstream infection (CRBSI) and a hemodynamically stable patient state in accordance with the type of microorganism isolated from blood culture.

The catheter must be removed in cases of:

1.       development of CRBSI with identification of Staphylococcus aureus, Gram-negative bacteria (Pseudomonas spp., Acinetobacter spp., Achromobacter spp., Stenotrophomonas maltophilia, etc.), or yeast-like/mold fungi.

2.       the following patient conditions:

•       severe sepsis;

•      hematogenous involvement of organs and tissues;

•      tunnel/pocket infection in tunneled and implanted CVCs;

•      suppurative thrombophlebitis;

•      endocarditis;

•      persistence of bacteremia/fungemia despite targeted antimicrobial therapy for more than 72 hours.

The catheter should not be removed if alternative venous access cannot be established in an emergency.

Indications for the removal of an established PVC (in children and adults) [175].

1.      there is no need for vascular access or the catheter has not been used for 24 hours or more,

2.      replacement of the catheter with another type due to a change in the treatment plan,

3.      complications of an established PVC (if a complication occurs with a long PVC or midline catheter, consider replacement over a guidewire):

•      catheter damage,

•      partial or complete catheter occlusion (withdrawal occlusion is not an indication for catheter removal),

•      extravasation/infiltration (aspirate contents from the catheter before removal),

•      local infection:

• the presence of erythema or tenderness alone is not an indication for PVC removal,

•      phlebitis, thrombophlebitis, thrombosis:

• in midline-associated thrombosis, systemic treatment using the in-situ catheter should be discussed,

•      catheter displacement:

• displacement of a PVC by less than 2 cm does not require intervention (if functional and uninfected); secure the catheter in its current position, use,

• a midline catheter displaced by more than 2 cm may be replaced over a guidewire (if uninfected),

•      fever occurring during a short infusion (1 hour) or shortly after the end of the infusion (within 30 min) (draw blood for blood cultures from the catheter before its removal),

4.      catheter inserted without adherence to aseptic technique (due to emergency indications) — must be removed as soon as possible, within 24–48 hours. Label any catheter inserted without aseptic technique.

Appendix B. Physician Action Algorithms

Fig. B1. Algorithm for initial radioisotope diagnostics in a patient with suspected neurogenic tumor.

Comments: If 123I-MIBG scintigraphy is not available, 18F-FDG PET/CT or other radioisotope imaging methods described in the "Diagnostics" section may be performed.

Fig. B2. Treatment algorithm for active surveillance patients.

Fig. B3. Treatment algorithm for intermediate-risk patients.

Fig. B4. Treatment algorithm for high-risk patients.

Appendix C. Patient Information

Neuroblastoma is a type of malignant tumor that occurs predominantly in early childhood. It arises from modified immature cells of the sympathetic nervous system.

Neuroblastoma primarily occurs in early childhood, being the most common solid tumor in infants under 1 year of age, accounting for approximately one in every five diagnoses of cancer cases in this age group.

Neuroblastoma can develop anywhere there is nervous tissue of the sympathetic nervous system. Most commonly, it arises in the adrenal medulla and in the nerve plexuses on either side of the spinal column along the sympathetic trunk. When neuroblastoma originates in the sympathetic trunk, the tumor can appear in any segment along the spine — in the abdomen, pelvis, chest, and neck. Most frequently (in approximately 70% of all cases), the tumor is located in the abdomen (e.g., in the retroperitoneal space) — about half of such tumors are localized in the adrenals. Approximately one-fifth of neuroblastomas are detected in the chest and neck regions.

At the onset of the disease, many children with neuroblastoma may have no symptoms at all. The tumor is often discovered incidentally, for example, during a routine pediatric examination. Typically, symptoms appear when the tumor reaches a large size (when located in the retroperitoneal space, complaints of abdominal pain may occur; in the mediastinum, cough and shortness of breath) or when distant metastases develop (leg pain, weakness, loss of appetite, fever, blood abnormalities such as anemia, etc.). Neuroblastoma can mimic other diseases (ARVI, bronchitis, intestinal infection). Therefore, it is sometimes very difficult to suspect neuroblastoma based on clinical data alone.

If neuroblastoma is suspected, the child must be evaluated by a pediatric oncologist/hematologist and scheduled for an in-depth workup. The main diagnostic methods include ultrasound, CT, or MRI of the chest and abdomen, bone marrow aspirations, and assessment of tumor markers (NSE, ferritin, LDH). An important diagnostic modality for neuroblastoma is radioisotope imaging — 123I-MIBG scintigraphy.

Histological examination to confirm the diagnosis of neuroblastoma can be performed after surgical intervention (tumor resection or biopsy). In this procedure, a small tissue sample is obtained. Biopsy is performed via surgery under general anesthesia, in which a portion of the tumor (primary or, in some cases, its metastases) is sampled through a small incision.

Following histological confirmation of neuroblastoma, molecular genetic testing will be performed to identify unfavorable tumor genetic markers.

Once all diagnostic results are obtained, the stage of the disease and risk group will be established, and a management plan for the child will be determined. Treatment tactics depend on the risk group. The risk group is determined by age, tumor characteristics (histology and genetics), and stage (extent of disease spread). Currently, three risk groups are distinguished: low risk (observation), intermediate risk, and high risk.

In the observation group, the physician may limit intervention to surgery alone, and chemotherapy may be required only in the presence of conditions threatening the child's life (massive liver metastasis, tumor extension into the spinal canal).

Intermediate- and high-risk patients receive intensive therapy, which includes courses of chemotherapy, surgery, radiation therapy, and, for high-risk patients, high-dose chemotherapy followed by autologous hematopoietic stem cell transplantation (auto-HSCT).

Along with the administration of chemotherapy drugs, the physician will prescribe supportive care — antibiotics, medications to increase blood leukocyte levels, antiemetics, and blood components. All of these are necessary to reduce and manage the side effects of chemotherapy.

Upon completion of specific therapy, the child will undergo a complete workup designed to assess the tumor response to the treatment. Subsequently, a schedule for follow-up monitoring and examinations will be established.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

Appendix G1. Karnofsky Performance Scale Assessment

Russian title: Karnofsky Performance Scale.

Original title: Karnofsky Performance Status.

Source (official developer website, validation publication):

Karnofsky D.A., Burchenal J.H. The clinical evaluation of chemotherapeutic agents in cancer. In: MacLeod C. (ed.). Evaluation of chemotherapeutic agents. New York: Columbia University Press; 1949:191–205 [45].

Type: rating scale.

Purpose: to describe the patient's level of functioning in terms of their ability to care for themselves, daily activities, and physical abilities (walking, work, etc.).

Table 48. Karnofsky Performance Scale