Five-Year Results of a Prospective Phase 2 Trial Evaluating Three-Week Hypofractionated Whole Breast Radiotherapy Inclusive of a Sequential Boost
Mené sur 146 patientes atteintes d'un cancer du sein de stade 0 à IIIA (âge médian : 54 ans ; durée médiane de suivi : 62 mois), cet essai de phase II évalue l'efficacité, du point de vue du contrôle locorégional, et la toxicité d'une radiothérapie hypofractionnée de l'ensemble du sein suivie d'une radiothérapie de type "boost" ciblant le lit tumoral
Résumé en anglais
Purpose : To report five-year outcomes of a phase 2 trial of hypofractionated whole breast irradiation (HF-WBI) completed in three weeks inclusive of a sequential boost.
Methods and Materials : Women with Stage 0-IIIA breast cancer (DCIS through T2N2a) were enrolled on a prospective, phase 2 trial of accelerated HF-WBI. We delivered a whole breast dose of 36.63 Gy in 11 fractions of 3.33 Gy, with an equivalent dose to the regional nodes (RNI) when indicated, followed by a tumor bed boost of 13.32 Gy in 4 fractions of 3.33 Gy over a total of 15 treatment days. The primary endpoint was locoregional control; secondary endpoints included acute/late toxicity and physician-assessed and patient-reported breast cosmesis.
Results : Between 2009 and 2017 we enrolled 150 patients, of whom 146 received the protocol treatment. Median age was 54 years (range, 33-82) and median follow-up was 62 months. Patients with higher-risk disease comprised 59% of the cohort, including features such as young age (33% ≤50 years), positive nodes (13%), and triple-negative disease (11%), and treatment with RNI (11%) and/or neoadjuvant/adjuvant chemotherapy (36%). Five-year estimated locoregional and distant control were 97.7% (95% confidence interval [CI], 93.0%-99.3%) and 97.9% (95% CI, 93.6%-99.3%), respectively. Five-year breast cancer-specific and overall survival were 99.2% (95% CI, 94.6%-99.9%) and 97.3% (95% CI, 91.9%-99.1%), respectively. Acute/late grade 2 and 3 toxicities were observed in 30%/10% and 1%/3% of patients, respectively. There were no grade 4 or 5 toxicities. Physicians assessed breast cosmesis as good or excellent in 95% of patients; 85% of patients self-reported slight to no difference between the treated and untreated breast.
Conclusions : Our phase 2 trial offers one of the shortest courses of HF-WBI; at five years of follow-up there continues to be excellent locoregional control and low toxicity with favorable cosmetic outcomes in a heterogeneous cohort of patients.
