ESTRO 2025 - Abstract Book

S434

Clinical - Breast

ESTRO 2025

Conclusion: PMRT led to more local symptoms up to 5 years post randomisation, but the difference is small, and there was no impact on other pre-specified QOL domains. Other patient (baseline score and age) and treatment factors (surgery and systemic therapy) impacted QOL scores independent of radiotherapy administration. These data will inform shared decision making when chest wall radiotherapy is being considered post mastectomy.

Keywords: Quality of Life, mastectomy, chest wall RT

474

Digital Poster Ultra-Hypofractionated Risk-Adapted Whole Breast Radiotherapy with Moderately Hypofractionated Sequential Boost: Early and Intermediate Outcomes Olga Unterkirhere 1 , Tino Streller 1 , David Jeller 1 , Philippe Logaritsch 1 , Susanne Bucher 2 , Peter Dubsky 3,4 , Christoph Glanzmann 1 , Gabriela Studer 1,4 1 Radiation Oncology, Kantonsspital Luzern, Luzern, Switzerland. 2 Breast Center, Kantonsspital Luzern, Luzern, Switzerland. 3 Tumour- and Breast Cancer Centre, Hirslanden Klinik St. Anna, Luzern, Switzerland. 4 Faculty of Health Sciences and Medicine, University of Lucerne, Luzern, Switzerland Purpose/Objective: This prospective, single-institution study evaluates the early and intermediate treatment tolerance in patients receiving adjuvant ultra-hypofractionated, risk-adapted whole breast radiotherapy (uhWBRT), with or without a moderately hypofractionated sequential boost, following breast-conserving surgery. Material/Methods: uhWBRT was introduced at our institution in March 2020. Data from 605 patients without an indication for lymphatic irradiation were analyzed, including 524 patients with invasive carcinomas (pT1–pT3) and 81 patients with ductal carcinoma in situ (DCIS). The mean patient age was 63.1 years (range, 25.9–95.3 years). Acute reactions were assessed at the completion of radiotherapy and 2–3 weeks later. Late effects and patient-reported outcomes (PROMs) were evaluated 6 months post-radiotherapy and annually thereafter. Prescribed doses for uhWBRT and the boost were as follows: • Group 1: 26 Gy in 5 daily fractions plus a boost of 10.0–12.5 Gy in 4–5 daily fractions (338 patients, 55.9%). • Group 2: 26 Gy in 5 daily fractions without a boost (98 patients, 15.9%). • Group 3: 28 Gy in 5 fractions delivered twice per week without a boost (171 patients, 28.2%): for patients with high-risk features for whom boost administration was not possible.

Results: At radiotherapy completion, acute toxicity was Grade 0 in 30.9%, Grade 1 in 59.2%, and Grade 2 in 9.9% of patients.