ESTRO 2025 - Abstract Book

S524

Clinical - Breast

ESTRO 2025

Material/Methods: Inclusion criteria: early stage BC, age ≥ 18 years, BCS. Exclusion criteria: nodal RT, previous malignancy. Treatment: WBI (26 Gy in 5 fr); boost (according to risk factors, sequential or simultaneous integrated). Primary outcome: acute and late toxicity (CTCAE v5.0). Secondary outcomes: OS, DFS, LR, regional relapse and distant metastasis, cosmesis (Harvard Scale and photographic documentation 2 ) and QoL (EORTC-QLQ-C3 and -BR23). Results: From March 2020 to September 2024, 25 Italian centers enrolled 1798 patients (median age 71 years, range 19-93). 68.1% of the enrolled patients had invasive carcinomas; tumors were G1-G2 in 79.3% of cases and Luminal A in most cases. Pathological stage was T1 in 76.8% of cases and N0 in 80.3%. In most cases a boost dose was not prescribed, 80.7% of patients received endocrine therapy. Median follow up was 12 months (range 1-55). Acute (registered at 1 month after RT) and late (registered at 6, 12, 24, 36 and 48 months after RT) toxicities are reported in Table 1. Toxicity was related with pts’ age, tumor’s characteristics, systemic therapies, boost administration and dosimetric data. Significant results in bivariate and multivariate analyses are reported in Table 2. Three patients experienced in breast events (two of them had also nodal relapse), one patient only nodal relapse. In seven patients distant metastasis occurred and twenty-nine patients developed other tumors; fifteen patients died, one due to BC.