Radiation Risks and Screening Outcomes in DBT + SM vs DM: Insights from TOSYMA Trial

Overview

The TOSYMA trial compared radiation doses between digital breast tomosynthesis plus synthesised mammography (DBT + SM) and digital mammography (DM) across breast densities and age groups. Despite higher radiation doses with DBT + SM, improved cancer detection suggests a favorable benefit-risk ratio, particularly for women with dense breasts.

Background

Digital breast tomosynthesis combined with synthesised mammography (DBT + SM) is an emerging screening modality that may improve cancer detection compared to standard digital mammography (DM). Radiation exposure and associated lifetime attributable risk (LAR) remain important considerations in screening strategies. The TOSYMA trial was designed to assess breast dose differences between DBT + SM and DM in a real-world population screening setting, incorporating devices from multiple vendors. Economic and long-term outcome analyses were beyond the initial scope but are recognized as important future research areas.

Data Highlights

The TOSYMA trial demonstrated higher breast radiation doses for DBT + SM compared to DM across breast density categories and age groups. The synthetic mammography (SM) images were reconstructed from DBT data without additional radiation exposure. National dose reference levels (DLR) for DBT were updated in Germany in 2023 based on TOSYMA data, reflecting real-world device variability.

Key Findings

• The trial applied the linear no-threshold (LNT) model to estimate radiation-related lifetime attributable risk (LAR), consistent with radiation protection principles.
• DBT + SM delivers higher breast doses than DM but may offer improved cancer detection, especially in women with dense breasts, suggesting a favorable benefit-risk ratio.
• Economic evaluations and cost-effectiveness analyses were not part of the original trial but are essential for future implementation decisions.
• TOSYMA is a pragmatic randomized controlled trial embedded in population screening, using certified mammography devices from various vendors to enhance generalizability.
• The synthetic 2D mammography images were generated from DBT data without additional radiation, clarifying misconceptions about double exposure.
• Ongoing TOSYMA-2 study aims to evaluate interval cancer rates and cumulative 2-year breast cancer incidence, including advanced cancers, to assess clinical outcomes further.

Clinical Implications

Clinicians should consider that while DBT + SM involves higher radiation doses than DM, the improved detection rates may justify its use, particularly in women with dense breast tissue. The real-world variability in device radiation doses underscores the importance of adhering to updated national dose reference levels. Future screening strategies should integrate emerging technologies and risk-adapted approaches to optimize benefit-risk balance.

Conclusion

The TOSYMA trial provides important evidence supporting the use of DBT + SM in breast cancer screening, balancing higher radiation exposure against improved detection, especially in dense breasts. Continued research including economic analyses and long-term outcomes is warranted to guide implementation.

References

1. TOSYMA Trial Authors 2023 -- Comparing Radiation Risks and Screening Outcomes of DBT and Mammography
2. BEIR VII Committee 2006 -- Health Risks from Exposure to Low Levels of Ionizing Radiation