Cardiac Risk After Heart-Sparing Breast Radiotherapy

Area of Science:

• Cardiology
• Radiation Oncology
• Oncology

Background:

• Breast cancer radiotherapy can lead to cardiac events due to incidental heart radiation.
• Whole-heart radiation dose metrics are commonly used, but dose to the left anterior descending coronary artery (LAD) may be a better predictor of cardiac risk.

Purpose of the Study:

• To compare the predictive ability of heart and LAD radiation dose metrics for cardiac risk following breast radiotherapy.

Main Methods:

• A cross-sectional study analyzed data from 4908 breast cancer patients treated between 2008-2018.
• Cardiac events and coronary artery disease (CAD) were assessed via longitudinal follow-up.
• Receiver operator characteristic curves and competing-risks regression were used to analyze dose metrics, adjusted for cardiovascular risk factors.

Main Results:

• Among 2223 patients with left-sided breast cancer, maximum LAD dose (concordance index=0.58) better predicted cardiac events than mean heart dose (concordance index=0.53).
• A maximum LAD dose of 12 Gy EQD2 was identified as a risk stratification threshold.
• Higher maximum LAD dose (≥12 Gy EQD2) was independently associated with increased cardiac risk (SHR=1.81), while mean heart dose (≥2 Gy EQD2) was not.

Conclusions:

• Left anterior descending coronary artery (LAD) radiation dose is a significant predictor of cardiac events after breast radiotherapy, outperforming whole-heart metrics.
• Findings support LAD-based radiotherapy planning and respiratory motion management to mitigate long-term cardiovascular risks in breast cancer patients.