Utilization of Hypofractionated Whole-Breast Radiotherapy With Concurrent Anti-Human Epidermal Growth Factor Receptor 2 (HER2) Therapy.

Hypofractionated radiotherapy (Hypo-RT) is now considered the standard of care for the majority of patients receiving whole-breast irradiation (WBI). However, there are few data on the use of Hypo-RT in human epidermal growth factor receptor 2 (HER2)-positive patients receiving concurrent anti-HER2 therapy. In this study, we sought to examine patterns of WBI in HER2-positive patients. Using the National Cancer Data Base, we identified women with nonmetastatic HER2-positive breast cancer diagnosed between 2010 and 2015 who received WBI. The Hypo-RT group was defined as those receiving 21 or fewer fractions. All other patients were in the conventional radiotherapy (RT) group. Multivariate logistic regression was used to identify predictors of Hypo-RT utilization. Five-year overall survival was estimated by the Kaplan-Meier method. The study included 15,776 patients, of whom 17.7% received Hypo-RT. The rate of Hypo-RT utilization increased from 7.4% in 2010 to 29.3% in 2015 (P = .004). Predictors of Hypo-RT use included older age (≥60 vs. < 60 years), higher median income quartile, further distance from the treatment facility (>50 vs. ≤50 miles), treatment at an academic facility, and later year of diagnosis. Unadjusted 5-year overall survival rates were similar among patients who received Hypo-RT and conventional RT (93.9% vs. 95.2%, P = .26). After adjusting for patient, facility, and tumor variables, Hypo-RT was not significantly associated with survival. Although Hypo-RT was not commonly delivered in patients with HER2-positive breast cancer, the utilization rate quadrupled over the study period. Multiple socioeconomic and clinical predictors of Hypo-RT receipt were identified. Adjuvant RT regimen was not significantly associated with overall survival.

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