1187 Impact of the FIGO 2023 staging system for endometrial cancer in a large cohort from an Italian referral center

Introduction/Background In 2023, the FIGO Women's Cancer Committee released a novel staging system. The newly introduced system transitioned from a dissemination-based approach to one encompassing prognostic factors such as histotype, grading, and lymphovascular space invasion (LVSI). Additionally, the integration of molecular classification, when available, is a key feature of this updated system. This study aims to describe the application of the new staging system in a large population from a referral center. Methodology Consecutive patients with endometrial cancer who underwent surgery at the European Institute of Oncology, Milan, Italy, from April 2019 to December 2022 were included. All patients underwent comprehensive surgical staging with available histologic reports and complete molecular evaluations. We applied the 2023 FIGO staging system with and without the molecular classification and compared the results with those of the 2009 FIGO staging system. Results A total of 381 patients who met the inclusion criteria were included in the analysis. The mean age at diagnosis was 61.1 years (SD ± 12.2). A total of 335 tumors (87.9%) had endometroid histology, 273(71.6%) were classified as low-grade (G1-G2), LVSI was absent or focal in 330 cases (88.2%), and myometrial invasion was greater than 50% in 121 cases (31.9%). A total of 163 patients (42.8%) were classified as NSMP, 113(29.7%) as MMRd, 69(18.1%) as p53abn, and 36(9.4%) as POLEmut. Patient allocation according to different staging systems is presented in Table 1. Transitioning from the 2009 to 2023 staging system, without molecular analysis integration, resulted in 60(15.7%) patients being upstaged and 13(3.4%) being downstaged. After incorporating molecular analysis into the 2023 staging system, 6(2.1%) patients were upstaged, while 11(4.2%) were downstaged. Conclusion The new FIGO staging system has considerably reshaped the classification of endometrial cancer. Updated guidelines on the adjuvant treatment integrating this novel staging system are expected to apply it into the clinical practice. Disclosures Nothing to disclose.