ESTRO 2025 - Abstract Book

S1274

Clinical – Lower GI

ESTRO 2025

1 RADIATION ONCOLOGY, HUPM, CADIZ, Spain. 2 Anesthesiae, HUPR, CÁDIZ, Spain. 3 INiBICA, HU JEREZ, JEREZ DE LA FRA., Spain

Purpose/Objective: To evaluate overall survival (OS), disease-free survival (DFS), and prognostic factors in patients with locally advanced rectal cancer treated with hypofractionated radiotherapy under real-world care conditions, specifically analyzing the impact of total neoadjuvant therapy (TNT). Material/Methods: A single-center retrospective study (n=142, 2017–2022) of patients with locally advanced rectal cancer treated with hypofractionated radiotherapy (25 Gy/5 fractions using VMAT). Clinical-pathological markers were analyzed, including age (mean: 65.89 years, SD: 11.78), sex (64.1% male), tumor height (43.7% middle third), TNM stage (80.9% stage III), MRC (54.2% positive), and pCR (35.2%), as well as biomarkers (IMS [1.4%], EGFR [3.7% mutated], BRAF [3.7% mutated], RAS [44.4% mutated]). Univariate and multivariate analyses were conducted. Median follow-up: 34.6 months. Results: Survival rates were as follows: 2 and 5 years DFS: 91.2% and 85.6%, respectively. 2 and 5 years OS: 94.9% and 86.5%, respectively. Patients who did not receive TNT (35.9%) had worse OS (HR=2.4, p=0.047). Tumor stage was the only independent prognostic factor for DFS in multivariate analysis, with a predominance of locally advanced disease (IIIA: 9.9%, IIIB: 29.6%, IIIC: 41.5%). Adjuvant chemotherapy (24.6%) influenced DFS only in univariate analysis.