Impact of Fraction Size on Cardiac Mortality in Women Treated With Tangential Radiotherapy for Localized Breast Cancer

Abstract

To determine whether fraction size affects the risk of cardiac mortality in women treated with adjuvant radiotherapy (RT) for left-sided breast cancer. A population-based retrospective study of women with a diagnosis of localized breast cancer treated with adjuvant RT in British Columbia from 1984 to 2000. Cases were identified from the British Columbia Cancer Agency database. Overall and cardiac-specific survival were compared for women treated with RT for left- vs. right-sided breast cancer. We analyzed the impact of age (<or=60 vs. >60 years) at diagnosis and RT fraction size (<or=2 vs. >2 Gy) on risk of fatal cardiac events. We identified 3,781 women with left-sided and 3,666 women with right-sided breast cancer who received adjuvant RT. Median follow-up was 7.9 years. There were 52 vs. 47 breast cancer deaths in women treated for left- and right-sided breast cancer, respectively. There was no significant difference in cardiac mortality for women <or=60 or >60 years of age who received adjuvant RT for left-sided vs. right-sided cancer. There was no difference in cardiac mortality for women who received adjuvant RT with fraction sizes <or=2 vs. >2 Gy for left- or right-sided cancer. There was no evidence for increased risk of cardiac mortality in women treated with adjuvant RT after a median follow-up of 7.9 years in our cohort. Hypofractionated adjuvant RT regimens did not significantly increase the risk of cardiac mortality.