Rationale and principles
Malignant liver tumors, specifically hepatocellular carcinoma (HCC), derive almost their entire blood supply from the hepatic artery. Healthy parenchyma, conversely, has a dual blood supply and is nourished primarily by the portal vein. This anatomical difference forms the foundation for intra-arterial interventions.
By injecting microparticles containing chemotherapeutic drugs (TACE) or radioactive isotopes (SIRT) via a catheter into the arterial bed, the physician achieves two goals: inducing ischemic necrosis of the tumor node and locally delivering the toxic agent. This reduces systemic side effects and preserves the function of the healthy portion of the organ.
Transarterial chemoembolization (TACE)
Chemoembolization is used to prolong survival, control carcinoid symptoms (in neuroendocrine metastases), or downstage the tumor prior to radical resection or transplantation (downstaging).
- Optimal candidates: Patients with preserved liver function, ECOG status 0–1, and no extrahepatic spread.
- Contraindications: Massive parenchymal replacement by tumor (over 50–75%), hepatic failure, advanced cirrhosis.
- Technique: The procedure requires prior high-quality angiography (DSA) for vascular mapping. The drug is administered slowly and as superselectively as possible via microcatheters to prevent emboli from reaching nontarget areas.
- Complications: The most frequent is postembolization syndrome (PES), which lasts 2–7 days and manifests as pain, fever, and nausea. It occurs due to massive tumor cell death and cytokine release. Severe complications (bile duct necrosis, abscesses, tumor rupture) occur in approximately 4% of cases.
Yttrium-90 radioembolization (SIRT)
Radioembolization is a form of local brachytherapy. Instead of cytotoxics, polymer or glass microspheres loaded with Yttrium-90 ($^{90}Y$)—a pure beta emitter with a half-life of 64.2 hours—are used. Because $^{90}Y$ causes severe radiation tissue damage, preparation for the procedure requires exceptional precision.
Mandatory planning stages:
- GI tract protection: Aberrant branches supplying the stomach and intestines (e.g., the gastroduodenal artery) are pre-embolized with metallic coils. This protects the gastrointestinal tract from radiation ulcers in case of microsphere reflux.
- Lung shunt assessment: Tumors frequently form arteriovenous fistulas. To ensure that radioactive particles do not travel to the lungs (which would cause radiation pneumonitis), technetium-labeled macroaggregated albumin ($^{99m}Tc-MAA$) is administered to the patient, followed by SPECT. If the shunt fraction exceeds 20%, SIRT is contraindicated.
Therapy is performed strictly on one liver lobe per session, with an interval of at least four weeks.
Evaluation of efficacy
Follow-up imaging (CT or MRI) is performed 6 weeks after the procedure. Classic WHO criteria are considered of low diagnostic value for response assessment. Instead, RECIST (one-dimensional measurements) or EASL (change in the volume of enhancing viable tumor tissue) criteria are used.
Statistics show that radioembolization is superior to chemoembolization in downstaging cancer (58% vs. 31%) and is associated with a lower rate of progression in the first year. However, some meta-analyses indicate that conventional TACE is associated with higher toxicity, yet may not surpass standard embolization without a chemotherapeutic agent (bland TAE) in efficacy.
Briefly: answers to topical questions
What are the contraindications to transarterial chemoembolization (TACE) of the liver?
Contraindications to transarterial chemoembolization are divided into absolute and relative, and also include specific clinical limitations.
- Absolute — liver failure, low functional reserve, advanced cirrhosis, tumor replacement of more than 50–75% of the parenchyma, widespread extrahepatic disease.
- Relative — portal vein thrombosis, Child-Pugh class C, encephalopathy, active gastrointestinal bleeding, refractory ascites, presence of TIPS, bilirubin > 5 mg/dL.
- Vascular limitations — tumor invasion of major vessels, pronounced arteriovenous shunting, presence of an arterioportal shunt, hepatofugal blood flow.
- Clinical limitations — ECOG status 2 and higher, Child-Pugh class B8 and higher, uncorrectable thrombocytopenia, coagulopathy, severe renal failure.
By what criteria is the radiological tumor response to chemoembolization evaluated?
The radiological tumor response to chemoembolization is evaluated using several standardized criteria systems.
- WHO (WHO) — two-dimensional perpendicular tumor measurements (a method recognized as poorly reproducible).
- RECIST (including RECIST 1.1) — one-dimensional measurements of solid tumors.
- mRECIST — modified criteria for assessing liver tumor involvement in the setting of cirrhosis.
- EASL — evaluation based on the percentage change in the volume of contrast-enhancing tumor tissue following treatment.
Which chemotherapy drugs are most frequently used in transarterial chemoembolization for hepatocellular carcinoma?
In the presented clinical case for TACE via microcatheter, a combination of cisplatin, doxorubicin, and mitomycin mixed with lipiodol was used.
Which specific arteries require prophylactic coil embolization prior to SIRT to protect the gastrointestinal tract?
To prevent radiation-induced injury to the gastrointestinal tract prior to Yttrium-90 administration, prophylactic coil embolization of arteries supplying normal tissues is performed. The following vessels are subject to occlusion:
- Gastroduodenal artery (GDA) — an artery supplying normal GI tissues.
- Left and right gastric arteries — arteries supplying normal GI tissues.
- Falciform artery (falciform artery) — an artery supplying normal tissues.
- Cystic artery (cystic artery) — an artery supplying normal tissues.
Proximal coil placement in these branches reliably protects the intestines from nontarget delivery of the radioisotope.
Class and exam questions
Why doesn't the entire liver suffer during chemoembolization?
Due to blood supply characteristics: the tumor receives blood almost exclusively from the hepatic artery, whereas the healthy parenchyma is nourished primarily by mixed blood from the portal vein.
What is postembolization syndrome?
This is the body's reaction to acute ischemic tumor necrosis and a massive cytokine release. It is accompanied by fever, pain in the right upper quadrant, and nausea; it typically resolves within 2–7 days with symptomatic therapy.
Why are metallic coils needed before radioembolization?
They are required for prophylactic occlusion of arteries supplying the gastrointestinal tract. This prevents nontarget delivery of radioactive microspheres into the stomach or duodenal wall.
What else to study on this topic
- Barcelona Clinic Liver Cancer (BCLC) staging system and treatment selection algorithms
- Methodology of using $^{99m}Tc-MAA$ to assess lung shunting
- RECIST and EASL criteria: analysis of tumor response evaluation systems
- Embolization for traumatic and spontaneous liver hemorrhages
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