Cardiac Substructure Dosimetry and Major Adverse Cardiac Events After Breast Radiotherapy: A 12-Year Cohort Study...

Area of Science:

• Oncology
• Cardiology
• Radiation Oncology

Background:

• Breast cancer radiotherapy can increase the risk of major adverse cardiac events (MACE).
• Identifying cardiac substructures most vulnerable to radiation is crucial for risk assessment.
• Long-term follow-up data are essential for understanding the late effects of radiotherapy on cardiac health.

Purpose of the Study:

• To pinpoint cardiac substructure dosimetric predictors of MACE after breast radiotherapy.
• To develop a normal tissue complication probability (NTCP) model for personalized MACE risk assessment.
• To evaluate the impact of modern radiotherapy techniques on cardiac substructure doses and MACE risk.

Main Methods:

• Retrospective analysis of 633 female breast cancer patients treated with postoperative radiotherapy.
• Dose-volume metrics for the heart and six substructures were extracted and converted to EQD2.
• Fine-Gray regression identified MACE predictors; an NTCP model was built using LAD V40, age, and cardiac history.

Main Results:

• A median follow-up of 11.8 years revealed MACE in 4.6% of patients.
• Left anterior descending artery (LAD) V40 (dose to 40% of LAD volume) was the strongest MACE predictor (sHR=1.023 per %).
• An NTCP model incorporating LAD V40 demonstrated excellent discrimination (C-index=0.865); VMAT reduced LAD V40 and projected MACE risk by 5.7%.

Conclusions:

• LAD V40 is a superior predictor of MACE compared to whole-heart dosimetry in breast cancer patients.
• The developed NTCP model provides a framework for personalized cardiac risk stratification.
• Cardiac-sparing techniques, guided by LAD V40, can significantly reduce radiation-induced MACE.