Estimating risks from modern breast cancer radiotherapy: Implications for clinical decision-making, risk management and radiation protection

Addie Ivanova | Canadian Nuclear Safety CommissionEnoch ABC Ballroom

Breast cancer is the most common cancer among women in Canada. Adjuvant radiotherapy is received by most patients as part of their treatment, as it has been shown to reduce the risk of breast cancer recurrence and mortality. However, randomized trials have shown that breast cancer radiotherapy can also increase the risks of heart disease and second primary lung cancer and oesophageal cancer due to incidental radiation of the heart, lungs, and oesophagus, respectively. The absolute risks depend on radiation doses received by these organs at risk, and on the patients’ pre-existing risk factors.

To estimate these risks, a systematic review and meta-analysis was conducted of doses received by the heart, lungs, or oesophagus from radiotherapy in the United Kingdom for early breast cancer during 2015-2023. These values were then combined with values from dose-response relationships published in epidemiological studies to estimate absolute radiation-induced risks of heart disease, lung cancer, and oesophageal cancer. Risks were estimated considering various factors influential to organ dose received, including breast cancer laterality, clinical targets irradiated, and radiotherapy technique used, as well as pre-existing cardiac risk factors, and smoking status.

To inform clinical decisions, oncologists must weigh the absolute magnitude of the benefits from radiotherapy against the absolute magnitude of its risks for each patient. This research illustrates the importance of three considerations in patient treatment planning: patient selection (e.g., pre-existing cardiac risk factors, smoking status); cancer characteristics (e.g., laterality, localization/clinical targets); and application of modern radiotherapy techniques to limit radiation exposures to organs at risk (e.g., deep inspiration breath hold, proton therapy). The purpose of this presentation will be to present the findings of the systematic review and subsequent risk analysis, followed by an investigation on the implications to clinical decision-making, risk management, and radiation protection.

Thu 10:45 am - 12:00 pm