ESTRO 2025 - Abstract Book

S1180

Clinical – Lower GI

ESTRO 2025

compared to patients who had immediate TME at 18 months (17 vs 28, p=0.02) and 36 months (11 vs. 26, p<0.01). Wexner score showed significantly more fecal incontinence in patients with immediate TME compared to patients who remained TME-free at 6 months (7.5 vs. 3.1, p=0.003) and 12 months (7.8 vs. 3.2, p=0.003). Late grade 3/4 toxicity according to CTC-AE were more pronounced after immediate TME (13/53, 25%) as compared to patients with a sustained cCR (1/20, 5%). Conclusion: TNT with CRT and three cycles of FOLFOX resulted in three-year TME-free survival in approximately one fifth of the patients. Patients who remained TME-free showed less LARS, fecal incontinence, and late toxicity than patients with immediate TME.

Keywords: Organ preservation, rectal cancer, TNT

1760

Digital Poster Novel approach to rectal cancer in inflammatory bowel disease: preliminary results from a hyperfractionated-accelerated chemoradiation protocol. Nataliya Razganiayeva 1 , Alessandra Arcelli 2 , Dajana Cuicchi 3 , Alessandra Guido 2 , Arina A Zamfir 2 , Silvia Cammelli 2,1 , Giorgio Coco 1 , Maria Chiara Malato 1 , Francesco Di Fabio 4 , Fabiola L Rojas Llimpe 4 , Karim Rihawi 4 , Lidia Strigari 5 , Savino Cilla 6 , Matteo Rottoli 3,4 , Andrea Ardizzoni 4 , Gilberto Poggioli 3,1 , Alessio G Morganti 1,2 1 Department of Medical and Surgical Sciences, Alma Mater Studiorum University of Bologna, Bologna, Italy. 2 Radiation Oncology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy. 3 Surgery of the Alimentary Tract, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy. 4 Medical Oncology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy. 5 Department of Medical Physics, IRCCS Azienda Ospedaliero Universitaria di Bologna, Bologna, Italy. 6 Mediacal Physics Unit, Responsible Research Hospital, Gemelli Molise Hospital, Campobasso, Italy Purpose/Objective: This study aimed to evaluate the safety, efficacy, and outcomes of an accelerated hyperfractionated chemoradiotherapy regimen in patients with rectal cancer arising from inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis. Given the increased risk of gastrointestinal toxicity in this population, we sought to determine whether this approach could minimize late toxicities while maintaining effective neoadjuvant treatment. Material/Methods: We conducted an observational clinical study involving 10 patients with rectal cancer and underlying IBD treated at our institution between October 2020 and October 2023. All patients underwent a comprehensive pre-treatment evaluation by a multidisciplinary team, including staging with colonoscopy, CT, and MRI. Radiotherapy was planned using volumetric modulated arc therapy (VMAT) with a hyperfractionated-accelerated regimen: 39 Gy in 30 fractions (1.3 Gy per fraction) for PTV2 (pelvic nodes ad mesorectum) and 45 Gy in 30 fractions (1.5 Gy per fraction) for PTV1 (tumor), administered twice daily over approximately three weeks. Concurrent chemotherapy with capecitabine was given throughout the chemoradiotherapy (CRT) course. Surgical intervention was performed about eight weeks post-CRT, followed by regular follow-ups. Survival and toxicity outcomes were assessed using Kaplan-Meier survival analysis and the Common Terminology Criteria for Adverse Events (CTCAE), version 5. Results: The median follow-up was 36 months (range: 10-45 months). The cohort included 8 patients with Crohn's disease and 2 with ulcerative colitis, with a median age of 51 years. Tumor downstaging occurred in 7 of 10 patients, and 4 of 7 patients with nodal metastases experienced nodal downstaging. Three patients achieved a complete