Ultrahypofractionated Whole Breast Irradiation in Early-Stage Breast Cancer: An Italian Multicenter Observational...

In patients who received breast-conserving surgery 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 ultrahypofractionated schedule.

From 2020 to 2025, 2036 patients (median age 70 years; range, 19-93) were recruited from 28 Italian Radiation Oncology Centers. Inclusion criteria included: early-stage breast cancer (either invasive or ductal in situ carcinomas), age ≥ 18 years, breast-conserving surgery and delivery of ultrahypofractionated WBI by means of any radiation therapy (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 ≤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 months, 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 was associated with increased side effects. Significant risk factors for late side effects were active smoking at +6 months and a larger planning target volume boost at +6 and +12 months after the end of RT.

In our large series of patients with early-stage breast cancer, ultrahypofractionated WBI appeared safe and feasible.