ESTRO 2025 - Abstract Book

S1248

Clinical – Lower GI

ESTRO 2025

Conclusion: The primary endpoint was met with the lower limit of 90% CI >80% for 3-year LRF free rate with rd-IMRT. The shorter rd-IMRT regimen offers major advantages to patients, their carers, and health care systems and should be considered as a new treatment option for patients with early-stage anal cancer.

Keywords: anal cancer, phase II, radiotherapy

References: 1 Gilbert at al. Standard vs dose reduced chemoradiotherapy in anal cancer: short-term results of the PLATO-ACT4 RCT. Abstract OC-0831, ESTRO 2023 Annual meeting

3701

Digital Poster Unlocking Recovery: The Role of Dosimetry and Clinical Insights in Pelvic Floor Rehabilitation for Rectal Cancer Gloria Guardia López 1 , Gloria Sánchez Naranjo 1 , Pablo Alcaide Córdoba 1 , Mariana Temes Ramos 1 , Fernando García Luque 1 , Irene Alda Bravo 1 , Cristian Arias Guillen 1 , Carmen Peña Sánchez 1 , Rafael D'Ambrosi Centeno 1 , Elena Gómez Duque 1 , Luz Fiorella Huertas Campos 1 , Sandra Giselle Guardado González 1 , Sandra Fernández Alonso 1 , Laura Fernández Banda 1 , Nieves Gascón Costoso 1 , Sara Pedraza Fernández 1 , María Colmenero Hernández 1 , Francisco Mesa López 1 , Marta Manzano Rodriguez 2 , Jesus Vara 3 , Maria Ángeles Perez Escutia 1 1 Radiotherapy Oncology, Hospital Universitario 12 de Octubre, Madrid, Spain. 2 Radiophysics, Hospital Universitario 12 de Octubre, Madrid, Spain. 3 Physical Medicine and Rehabilitation, Hospital Universitario 12 de Octubre, Madrid, Spain Purpose/Objective: Neoadjuvant chemoradiotherapy followed by surgery is the standard for locally advanced rectal cancer (LARC), but its toxicity can impair anorectal function and quality of life. Pelvic floor rehabilitation has shown benefits in improving anorectal function. This study investigates clinical and dosimetric factors influencing the effectiveness of rehabilitation in these patients. Material/Methods: A retrospective study (2018-2023) analyzed patients with locally advanced rectal adenocarcinoma treated with neoadjuvant chemoradiotherapy (long- or short-course) followed by low anterior resection, +/- adjuvant chemotherapy. Physical Medicine and Rehabilitation assessed all patients using the Wexner anal incontinence scale before and after pelvic floor rehabilitation. Data on tumor characteristics, rehabilitation outcomes and treatment modalities (radiotherapy technique, anal sphincter doses) was collected. The anal sphincter contour was reviewed anatomically. Pre- and post-rehabilitation Wexner scores were compared, and statistical analysis was performed (p < 0.1). Results: From an initial cohort of 70 patients, 25 met all criteria (mean age 61, 68% male). 74% had tumors < 10 cm from the anal margin (53% middle and 21% lower rectum). None had sphincter infiltration, and only 5 had extramural venous extension. 76% received long-course chemoradiotherapy, and 24% received short-course radiotherapy. The mean of maximum sphincter dose was 28.39 (SD 18.50) Gy and a mean dose of 13.55 (SD 12.47) Gy (Figure1). All patients had ≤ G2 lower toxicity. Postoperative complications were seen in 36% of patients. Rehabilitation follow-up averaged 18 months, with 84% adherence. A trend toward improvement in anorectal function was observed (Figure 2). No significant differences were found in tumor characteristics. Short-course radiotherapy was associated with better rehabilitation outcomes (p = 0.07). Higher maximum and mean doses of radiation to the anal sphincter (p =