Accelerated Partial Breast Irradiation Using 5 Daily Fractions: A Prospective, Phase 2, Multicenter Trial of Cosmetic Outcomes and Toxicity—ACCEL Final Results

Abstract

PurposeTo investigate cosmetic degradation and toxicity for an APBI prescription delivered in five fractions over one week compared to WBI. MethodsThe trial is a multicentre, single-arm, phase II, prospective cohort study. Eligible women 50 years of age or older with ER-positive, HER2-negative, invasive ductal carcinoma or ductal carcinoma in situ after breast conserving surgery received 27 Gy in five daily fractions of APBI. The primary endpoint was non-inferiority of two-year cosmesis using the RAPID trial's WBI arm as the control arm. A global, consensus cosmetic score using the EORTC rating scale of excellent, good, fair, or poor for each patient at baseline and two-years was generated by a panel of five radiation oncologists using photographs of treated and untreated breasts. ResultsFrom 2016 to 2019, 298 eligible women were enrolled. By the two-year follow-up, 76 patients were lost or withdrew, and three had died, resulting in 219 patients available for complete, two-year photographic cosmetic evaluation. The median (interquartile range) follow-up for all participants was 4·7 years (3·8 – 5·5 years). No patient had a fair or poor cosmetic score at the two-year evaluation. Cosmesis was better or unchanged for 97% of patients, worse for 3% (excellent to good), and no cosmetic failures. The confidence intervals are 0·88 (0·86-0·90) and 1·00 (0·99-1·00) for the RAPID and ACCEL trials, respectively. ConclusionCosmetic degradation of five daily treatments of the ACCEL trial's APBI intervention is noninferior to the WBI arm of the RAPID trial.