The efficacy and safety of hypofractionated radiotherapy with concurrent anti‐HER‐2 therapy following breast‐conserving therapy for breast cancer

The purpose of this study was to report rates and severities of radiation‐related toxicities and analyze disease‐control outcomes in patients who have received hypofractionated whole breast radiation (HF) with concurrent trastuzumab with or without pertuzumab. We conducted a retrospective cohort study including women with stage I‐III HER2‐positive breast cancer who received HF at the University of Pennsylvania between 1/2005 and 5/2018 with concurrent trastuzumab with or without pertuzumab. Fractionation was 266 cGy daily to a total dose of 4256 cGy with or without a sequential tumor bed boost. Eighty patients were included in the cohort with a median follow‐up time of 21.44 months. There was one grade 3 acute toxicity (fatigue) and no grade 3 late toxicities. 91% and 25% of patients experienced grade 1‐2 acute and late skin reactions, respectively. An excellent‐good cosmetic outcome was reported by 74% and 95% of patients and physicians, respectively. No patients experienced tumor recurrences, and the only death was due to a secondary cause. These results suggest that hypofractionated whole breast radiation administered concurrently with anti‐HER‐2 therapies is efficacious and has acceptable toxicity in early‐stage breast cancer patients treated with lumpectomy. Continued follow‐up is warranted to evaluate long‐term outcomes.