One-Year Cosmesis and Fibrosis From ACCEL: Accelerated Partial Breast Irradiation (APBI) Using 27 Gy in 5 Daily Fractions

Purpose: To report 1-year cosmesis and toxicity outcomes of a prospective, phase II trial of accelerated partial breast irradiation using intensity-modulated radiation therapy (RT) to deliver 27 Gy in 5 daily fractions. Methods and Materials: Node-negative breast cancer patients after breast conserving surgery with clear excision margins, with physician-assessed excellent or good baseline cosmesis were invited to participate in a prospective clinical trial to receive 27 Gy in 5 daily fractions to the expanded primary site. Clinical photographs and European Organisation for Research and Treatment of Cancer cosmetic score were collected at baseline prior to RT and 1-year after radiation therapy. A protocol-specified, interim analysis was scheduled when 50 patients had completed 1-year followup. A panel of 6 physicians provided a consensus global cosmetic score (termed panel-assessed score) based on clinical photographs at baseline and 1-year. Fibrosis and telangiectasia were prospectively assessed by clinical research staff at clinic visits. Results: At the interim analysis, 55 patients had baseline and 1-year post-RT images available. Most patients had either an improvement (53%) or no change (40%) in cosmesis from baseline to 1-year. Among 49 patients with excellent or good panel-assessed score at baseline, only 2 (4%) patients had a fair score at 1-year post-RT, indicating cosmetic deterioration. No patients had evidence of telangiectasia or grade 2 or higher fibrosis. There were no recurrences. Conclusions: APBI using 27 Gy in 5 daily fractions achieved acceptable 1-year cosmesis and no grade 2 fibrosis. A preplanned stopping rule of 5% grade 2+ fibrosis was not observed. The trial will continue to the planned target accrual of 274 patients. Crown Copyright (C) 2019 Published by Elsevier Inc. on behalf of American Society for Radiation Oncology. All rights reserved.