LAD Dose Predicts Cardiac Risk After Breast Radiotherapy: JAMA

A new study published in the Journal of American Medical Association showed that while radiation exposure to the left anterior descending artery (LAD) was independently linked to cardiac events, whole-heart radiation exposure was not linked to cardiac risk at low levels.

Radiotherapy for breast cancer can inadvertently expose the heart to radiation, and previous data have indicated a rise in heart-related issues linked to the radiation dose. While whole-heart radiation metrics are typically used for evaluating risk, new findings propose that focusing on the radiation dose to the LAD might provide better insight into the risk. Hence, this research evaluated and compared how well heart and LAD radiation dose metrics can forecast cardiac risk following breast radiotherapy.

This was a cross-sectional analysis of breast cancer patients treated at a Canadian tertiary care facility between 2008 and 2018 using either intensity-modulated or three-dimensional conformal radiation. Patients with left-sided breast cancer were included in the main analysis. Longitudinal follow-up data were used to evaluate cardiac events. Dosimetry was converted to equivalent dose in 2-Gy fractions (EQD2) from computed tomography plans using automatic segmentation.

Myocardial infarction, hospitalization, or ER visits for unstable angina (also known as acute coronary syndrome), arrhythmia, heart failure, pericarditis, or myocarditis are examples of adverse cardiac events. Coronary artery disease (CAD) includes the incidence of coronary angiography and coronary revascularization. 2223 of the 4908 breast cancer patients in the analysis had left-sided breast cancer. The cumulative incidence of cardiac events or CAD was 5.0 at 10 years across a median (IQR) follow-up duration of 10.8 years.

The highest LAD dosage that best classified risk, according to a data-driven cut point study, was 12 Gy EQD2. Maximum LAD dosage outperformed mean heart dose in discriminating individuals with left-sided breast cancer. Maximum LAD of 12 Gy or more was independently linked to increased cardiac risk in multivariable analysis, although mean heart dosage of 2 Gy or more was not (P =.99).

In a clinical setting, a physical dosage of around 10.5 Gy for 42.5 Gy in 16 fractions and 7 Gy for 26 Gy in 5 fractions is equivalent to the 12-Gy EQD2 for maximal LAD dose. Overall, LAD dosage was linked to cardiac events in this cross-sectional research of heart-sparing breast radiation, while whole-heart measures were not.

Reference:

Quirk, S., Atkins, K. M., Logie, N., Miller, R. J. H., Guthier, C., Mak, R. H., Warren, L. E. G., Ramin, C., Al-Rashdan, A., Wright, J. L., & Roumeliotis, M. (2026). Cardiac risk after heart-sparing breast radiotherapy. JAMA Oncology, 12(9), 931–939. https://doi.org/10.1001/jamaoncol.2026.2066