1200 The significance of CTNNB1 mutation in endometrial cancer

Introduction/Background Previous studies have shown that CTNNB1 mutations increase the risk of recurrence in endometrial cancer (EC), particularly in the non-specific molecular profile (NSMP) subset.1 CTNNB1 is a β-catenin-encoding gene, and mutations are present in approximately 20–25% of EC. This study investigates clinicopathological differences between CTNNB1 mutated (CTNNB1mut) tumours and CTNNB1 wild type (CTNNB1wt) tumours, including progression free survival (PFS) and overall survival (OS) Methodology This retrospective analysis includes consecutive patients diagnosed with EC between February 2019 and December 2022 in the University Hospital Leuven. Next-generation sequencing was performed as part of the routine histopathological examination in all patients. Statistical analyses used the Mann-Whitney U test and Fisher exact test for group comparisons, and the Kaplan-Meier method with Cox proportional hazard regression for estimating survival. Results Among the cohort of 243 EC patients, 41 (16.9%) had a hotspot CTNNB1 mutation. CTNNB1mut EC was predominantly endometrioid (pConclusion CTNNB1mut tumours exhibit distinctive clinicopathological features. In contrast to previous publications, we were not able to show a survival difference between CTNNB1mut and CTNNB1wt EC, neither in the whole EC population, nor in the NSMP subgroup. Reference Travaglino, et al. Arch Gynecol Obstet 2022;306:423. Disclosures Charlotte Tuerlinckx: No disclosures Isabelle Vanden Bempt: No disclosures Anne-Sophie Van Rompuy: No disclosures Thaïs Baert: Grants/research funding: Roche. Honoraria/consultation fees: AstraZeneca, GSK, Lilly, Novartis. Other support: AstraZeneca, GSK, MSD (travel, accommodation, expenses). Fréderic Amant: No disclosures Siel Olbrecht: No disclosures Toon Van De Putte: No disclosures Els Van Nieuwenhuysen: Grants/research funding: Eli-Lilly. Honoraria/consultation fees: AstraZeneca, OncoInvent, Regeneron. Toon Van Gorp: Grants/research funding: AstraZeneca, Roche, Amgen; Honoraria/consultation fees: AstraZeneca, Eisai, GSK, MSD, ImmunoGen, Incyte, OncXerna Therapeutics, Seagen Tubulis, Zentalis; Speaker's bureau: AstraZeneca, GSK, ImmunoGen; Other support: AstraZeneca, GSK, ImmunoGen, MSD, PharmaMar, Roche (travel, accommodation, expenses).