Long-term risk of major cardiac events after IMRT or 3D-CRT for breast cancer: secondary analysis of a phase 3 study

Secondary analysis of the multicenter phase 3 KROG 15-03 study in South Korea found that after breast-conserving surgery and three-dimensional or intensity-modulated radiotherapy for breast cancer, the cumulative incidence of major cardiac events (MCEs) was 1.8% at 6.5 years. The incidence of MCEs was 1.1% in the subgroup with a mean heart dose (MHD) ≤ 2.9 Gy and 3.3% in the subgroup with MHD ≥ 2.9 Gy (p=0.010) and 0.9% in the subgroup of age ≤ 55 years and 3.3% in the subgroup of age > 55 years. Multivariate analyses confirmed that MHD (HR 1.21 per 1 Gy; p=0.044) and age (HR 1.07 per 1 year; p=0.034) were significant factors of MCEs.