Adjuvant Hypofractionated Versus Conventional Whole Breast Radiation Therapy for Early-Stage Breast Cancer: Long-Term Hospital-Related Morbidity From Cardiac Causes

Purpose The risk of cardiac injury with hypofractionated whole-breast/chest wall radiation therapy (HF-WBI) compared with conventional whole-breast/chest wall radiation therapy (CF-WBI) in women with left-sided breast cancer remains a concern. The purpose of this study was to determine if there is an increase in hospital-related morbidity from cardiac causes with HF-WBI relative to CF-WBI. Methods and Materials Between 1990 and 1998, 5334 women ≤80 years of age with early-stage breast cancer were treated with postoperative radiation therapy to the breast or chest wall alone. A population-based database recorded baseline patient, tumor, and treatment factors. Hospital administrative records identified baseline cardiac risk factors and other comorbidities. Factors between radiation therapy groups were balanced using a propensity-score model. The first event of a hospital admission for cardiac causes after radiation therapy was determined from hospitalization records. Ten- and 15-year cumulative hospital-related cardiac morbidity after radiation therapy was estimated for left- and right-sided cases using a competing risk approach. Results The median follow-up was 13.2 years. For left-sided cases, 485 women were treated with CF-WBI, and 2221 women were treated with HF-WBI. Mastectomy was more common in the HF-WBI group, whereas boost was more common in the CF-WBI group. The CF-WBI group had a higher prevalence of diabetes. The 15-year cumulative hospital-related morbidity from cardiac causes (95% confidence interval) was not different between the 2 radiation therapy regimens after propensity-score adjustment: 21% (19-22) with HF-WBI and 21% (17-25) with CF-WBI ( P =.93). For right-sided cases, the 15-year cumulative hospital-related morbidity from cardiac causes was also similar between the radiation therapy groups ( P =.76). Conclusions There is no difference in morbidity leading to hospitalization from cardiac causes among women with left-sided early-stage breast cancer treated with HF-WBI or CF-WBI at 15-year follow-up.