Ultra-hypofractionated whole breast irradiation in early-stage breast cancer: an Italian multi-centre observational study.

Abstract

In patients who received breast-conserving surgery (BCS) for early-stage breast cancer, the present study assessed acute and short-term side effects and oncological outcomes after whole breast irradiation (WBI) with an ultra-hypofractionated schedule. From 2020 to 2025, 2036 patients (median age 70 years, range 19-93) were recruited from 28 Italian Radiation Oncology Centres. Inclusion criteria were: early-stage breast cancer (either invasive or ductal in situ carcinomas), age ≥ 18 years, BCS, delivery of ultra-hypofractionated WBI by means of any radiotherapy (RT) technique. All patients received 26 Gy in 5 consecutive fractions of 5.2 Gy. Depending on risk factors for local relapse some patients received a sequential or simultaneous integrated boost. Side effects were monitored at diverse time-points for up to 2 years. Median follow-up was 12 months (range 1-55). The incidence of side effects was low and they were mainly G1. The most frequent acute side effect (37.1%) was erythema, 90.2% were G1. Skin hyperpigmentation, the most frequent short-term late side effect, occurred in 12.2% of patients (95.7% G1) at 6 months, in 5.7% (98.4% G1) at 12 months, 5.7% (96% G1) at 18 and 4% (100% G1) at 24 months after the end of RT. In multivariate analysis significant factors for acute side effects were active smoking and boost administration. Furthermore age emerged as a protective factor while a larger breast planning target volume (PTV) was associated with increased side effects. Significant risk factors for late side effects were active smoking at +6 months and larger PTV boost at +6 and +12 months after the end of RT. In our large series of early stage breast cancer patients ultra-hypofractionated WBI appeared safe and feasible.