Top Line: What is the optimal dose limit for left anterior descending coronary artery when planning left breast radiation?
The Study: Mean dose to the whole heart is widely utilized when planning radiation for left sided breast cancer. However, dose to the left anterior descending artery may be a better predictor of adverse cardiac outcomes if you’re easily meeting mean heart goals. This population based, cross sectional study identified 2223 left sided breast cancer patients who received adjuvant radiation between 2008 and 2018. Among the centers included, DIBH was instituted in 2013 for left sided cases, and utilization significantly increased over time. The authors defined an adverse cardiac event as an ED visit or hospitalization for unstable angina, arrhythmia, heart failure, pericarditis, or myocarditis. Coronary artery disease (CAD) was defined as undergoing coronary angiography or a revascularization procedure. The heart and substructures were contoured using automated segmentation, and heart doses were converted to equivalent dose in 2 Gy fractions (EQD2). At 10 years, the cumulative incidence of cardiac events or CAD was 5%. Overall, medical risk factors for or pre-existing cardiac disease were the overwhelming drivers of events. Recall that the field became very cognizant of heart dose during the time these patients were treated. Therefore, mean heart dose was low at 1-2 Gy EQD2 prior to DIBH and <1 Gy EQD2 after DIBH. As a result, mean heart dose was not strongly associated with the risk of cardiac events or CAD. The only measure of heart dose associated with cardiac events or CAD in multivariable analysis was maximum LAD dose. They identified an optimal threshold (granted discrimination was relatively weak, C index 0.58) for LAD max of 12 Gy EQD2, which is about 10.5 Gy in 15 fractions or 7 Gy in 5 fractions.
TBL: Even if you have low mean heart dose from left breast radiation with heart-sparing techniques, reducing LAD max dose could further reduce the risk of cardiac events especially among those with pre-existing CAD or cardiac risk factors. | Quirk, JAMA Oncol 2026
The Study: Mean dose to the whole heart is widely utilized when planning radiation for left sided breast cancer. However, dose to the left anterior descending artery may be a better predictor of adverse cardiac outcomes if you’re easily meeting mean heart goals. This population based, cross sectional study identified 2223 left sided breast cancer patients who received adjuvant radiation between 2008 and 2018. Among the centers included, DIBH was instituted in 2013 for left sided cases, and utilization significantly increased over time. The authors defined an adverse cardiac event as an ED visit or hospitalization for unstable angina, arrhythmia, heart failure, pericarditis, or myocarditis. Coronary artery disease (CAD) was defined as undergoing coronary angiography or a revascularization procedure. The heart and substructures were contoured using automated segmentation, and heart doses were converted to equivalent dose in 2 Gy fractions (EQD2). At 10 years, the cumulative incidence of cardiac events or CAD was 5%. Overall, medical risk factors for or pre-existing cardiac disease were the overwhelming drivers of events. Recall that the field became very cognizant of heart dose during the time these patients were treated. Therefore, mean heart dose was low at 1-2 Gy EQD2 prior to DIBH and <1 Gy EQD2 after DIBH. As a result, mean heart dose was not strongly associated with the risk of cardiac events or CAD. The only measure of heart dose associated with cardiac events or CAD in multivariable analysis was maximum LAD dose. They identified an optimal threshold (granted discrimination was relatively weak, C index 0.58) for LAD max of 12 Gy EQD2, which is about 10.5 Gy in 15 fractions or 7 Gy in 5 fractions.
TBL: Even if you have low mean heart dose from left breast radiation with heart-sparing techniques, reducing LAD max dose could further reduce the risk of cardiac events especially among those with pre-existing CAD or cardiac risk factors. | Quirk, JAMA Oncol 2026