One-year cosmesis and fibrosis from XXXX: Accelerated Partial Breast Irradiation (APBI) using 27 Gy in 5 daily fractions

Abstract 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 follow-up. 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.