Hypofractionated whole breast irradiation after conservative surgery for patients aged less than 60 years: a multi-centre comparative study

Background: For decades, conventional fractionated whole breast irradiation (CF-WBI) was used after breast conserving surgery (BCS). Pivotal phase-3 trials on hypofractionated-WBI (HF-WBI) showed its non-inferiority as compared to CF-WBI. However, younger patients are often not treated with HF-WBI. The aim of this multi-centre comparative study is to confirm the safety of HF-WBI in a real-life series of younger patients. Material and methods: Between 2010 and 2016, a total of 786 patients aged less than 60 years old with early-stage breast cancer were treated with postoperative WBI after BCS in three breast cancer centres: 340 underwent HF-WBI while 446 were treated with CF-WBI. Acute toxicity was evaluated at the end of WBI. Late toxicity was evaluated at 6, 12, 24 and 36 months. Results: At univariate logistic analysis, hypofractionation showed a significant protective effect in terms of acute oedema, acute wet desquamation, chronic oedema, chronic erythema/pigmentation and breast fibrosis. At multivariate logistic analysis, hypofractionation was an independent significant factor for acute oedema, acute wet desquamation, and chronic oedema. There were not differences in tumour-related outcomes. Conclusions: HF-WBI showed significantly improved outcomes in terms of acute skin oedema, wet desquamation and chronic skin oedema. HF-WBI after BCS should be strongly encouraged to replace CF-WBI independently of age.