ESTRO 2025 - Abstract Book

S1266

Clinical – Lower GI

ESTRO 2025

4050

Digital Poster Induction or consolidation strategy in total neoadyuvant therapy?

Irene Alda Bravo, Gloria Guardia López, Gloria Sánchez Naranjo, Carmen Peña Sánchez, Rafael D'Ambrosi Centeno, Maria Colmenero Hernández, Nieves Gascón Costoso, Cristian Arias Guillén, Eduardo Cabello Murillo, María Ángeles Pérez Escutia Radiotherapy Oncology, Hospital Universitario 12 de Octubre, Madrid, Spain Purpose/Objective: Total Neoadjuvant Therapy (TNT) has marked a paradigm shift in locally advanced rectal cancer (LARC). This consists of administering systemic treatment in the neoadjuvant phase, either before (induction, iCT) or after (consolidation, cCT) short/large course of radiotherapy. This study aims to show the experience in our center. Material/Methods: Restrospective study between 2017-2022. 79 patients with LARC treated with TNT were collected and follow-up until May 2024. Both strategies were compared in terms of intra-treatment progression, clinical, pathologic response and overall (OS) and disease-free survival (DFS). Results: Intra-treatment progression was observed in 5% of the iCT, however, there were no cases in the cCT group. Regarding acute toxicity G3-4: gastrointestinal, genitourinary and hematological toxicity were superior in iCT than cCT (4,5% vs 0%; 9% vs 3%; 7% vs 0%; respectively). Eighteen patients showed complete clinical response; performing a non-surgical strategy in 9. Within these, 56% received cCT, 88% long course of radiotherapy and 75% were in the lower rectum. Twelve of the total patients had complete pathological response, 58% in iQT group and 42% in cCT, without significant differences; 75% were in the lower/medium rectum. Comparing T clinical with T pathological in cCT groups, Fisher =0.006 in favor of consolidation therapy, so better response after surgery was observed in this group. Postoperative complications were similar regardless of treatment scheme used. Survival outcomes: OS at 6-years were 81%; DFS al 6-years were 76% for cCT whereas 69% for iQT with p-value no statistically significant.