The Feasibility of Radiation Therapy after Breast-Conserving Surgery for Multiple Ipsilateral Breast Cancer: An Initial Report from ACOSOG Z11102 (Alliance) Trial

PURPOSE: Historically, multiple ipsilateral breast cancer (MIBC) has been a contraindication to breast-conserving therapy. We report the feasibility of radiation therapy (RT) after breast-conserving therapy in MIBC from the Alliance Z11102 trial. METHODS AND MATERIALS: Delineation of targets and organs at risk was performed according to the Radiation Therapy Oncology Group contouring consensus definitions. RT was delivered to the whole breast to 45 to 50 Gy in standard daily fractions of 1.8 to 2.0 Gy. A boost of 10 to 16 Gy in 2.0-Gy daily fractions to each tumor bed was mandatory. RESULTS: A total of 236 eligible patients were enrolled in the study between July 23, 2012 and August 19, 2016. Of those, 195 (83%) completed RT. No patient underwent mastectomy for failure to meet the RT dose constraints. Higher absolute boost volume was associated with increased incidence of grade 2 or higher dermatitis (odds ratio, 1.21; 95% confidence interval, 1.041.41; P = .014). Higher relative boost volume as a percentage of the overall breast volume was not associated with increased dermatitis. Neither absolute nor relative boost volume appeared to significantly influence overall cosmesis. CONCLUSIONS: Breast conservation followed by whole breast RT plus boost to each tumor bed was feasible in the majority of patients with MIBC. Increasing radiation boost volume was associated with increased incidence of acute dermatitis, but was not associated with worse overall cosmesis.