Breast tomosynthesis

Clinical advantages of tomosynthesis

Standard 2D mammography has a significant limitation: tissue summation shadows can obscure certain pathologies. On conventional images, a physician may only notice ambiguous areas of architectural distortion.

The use of digital breast tomosynthesis (Digital Breast Tomosynthesis, DBT) allows the breast volume to be split into individual slices, making it possible to clearly identify hidden threats. For example, where a 2D image shows only an unclear deformation, DBT can reveal multiple separate spiculated masses, fundamentally changing patient management tactics (e.g., confirming multifocal carcinoma followed by mastectomy after ultrasound-guided biopsy). Tomosynthesis is particularly effective in detecting spiculated lesions, which often correspond to low-grade malignancies.

Impact on screening metrics

The implementation of DBT significantly affects key statistical metrics of screening programs. A large-scale North American study (Friedewald et al., 2014) encompassing approximately half a million examinations demonstrated:

• Increased detection rate: The cancer detection rate increased from 4.2 to 5.4 cases per 1,000 examined women (a 29% increase).
• Reduction in recalls: The frequency of so-called recall rates (situations where a patient is asked to return for additional evaluation) decreased from 10.7% to 9.1%.

It is worth noting that the method's efficacy depends on the baseline screening system. In clinics with a traditionally high recall rate (over 10%, typical for single-reading systems), tomosynthesis demonstrates a pronounced positive effect. Conversely, in systems with initially low recall rates (e.g., with double-blind reading), the results of DBT remain contradictory.

Challenges and limitations

Despite its high sensitivity, the widespread use of DBT in screening is associated with several serious issues:

1. Overdiagnosis (Over-diagnosis): The increased detection rate is often driven by the identification of small, indolent, and slow-growing tumors with which a patient could live safely for years without clinical manifestations.
2. The interval cancer issue: It was anticipated that a more accurate method would reduce the number of cancers arising between routine screenings. However, the Oslo DBT screening trial (2018) did not reveal a significant change in this metric.
3. Impact on survival: To date, there is insufficient clinical evidence that tomosynthesis reliably reduces breast cancer mortality.

Why is a 2D component necessary?

Even when performing cross-sectional tomosynthesis, the conventional 2D image remains mandatory. It is necessary for an adequate assessment of breast symmetry, detection of microcalcifications (where DBT is less reliable), and comparison with prior mammograms.

A 2D image can be obtained in two ways:

• Combined mode (Combo mode): The machine performs two separate exposures (2D and DBT) under a single breast compression. The main drawback is the doubling of the radiation dose, which is highly undesirable for mass screening of healthy women.
• Synthesized mammogram: Special algorithms artificially generate a 2D image based on the tomosynthesis dataset. No additional radiation is required, and clinical trials have proven that such images are equivalent in diagnostic value to standard scans.

Logistics and alternatives

Transitioning a clinic to tomosynthesis requires substantial resources. First, the interpretation time per examination increases at least twofold, overloading radiologists. Second, the massive volume of files requires upgrading storage systems (PACS), and the equipment itself must be replaced. The future of the method will be determined by ongoing major trials (PROSPECTS, TMIST), which are designed to assess its cost-effectiveness.

An alternative approach to increasing the sensitivity of conventional 2D mammograms is contrast-enhanced spectral mammography (CESM). This method involves the intravenous administration of an iodine-based contrast agent to evaluate tumor vascularity, which is particularly relevant for young patients with high breast tissue density.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Methodology and indications for ultrasound-guided biopsy
• Contrast-enhanced spectral mammography (CESM)
• Radiological patterns of microcalcifications
• Organization of medical image storage (PACS) and DICOM workflows
• Histological classification of breast carcinomas

Other topics in the "Diagnostic Radiology in Oncology" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.