Differentiation of survival outcomes by anatomic involvement and histology with the revised 2023 International Federation of Gynecology and Obstetrics staging system for endometrial cancer

Objectives: The International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial cancer underwent revision in 2023, incorporating histology, lymphovascular space invasion, and molecular classification. Herein, we compare overall survival (OS) outcomes by anatomic and histologic involvement for patients staged by the 2009 system versus 2023 system. Methods: The National Cancer Database (NCDB) was queried for patients with newly-diagnosed uterine adenocarcinoma from 2004 to 2015, with follow-up data extending through 2020. Stage was determined by both the 2009 and 2023 FIGO staging systems. Kaplan-Meier estimators and Cox proportional hazards models were used for survival analysis. Results: A total of 134,677 patients were analyzed. Per 2023 classification, patients with stage I disease decreased from 96,161 to 70,101 (-27.1%, p < 0.01), while stage II disease increased from 9295 to 36,294 (+390.5%, p < 0.01). Greatest OS change was observed for 2023 stage IA3 patients (low-risk, synchronous endometrial and ovarian tumors with a clonal relationship), whose 10-year OS was 73.4%, compared to 52.6% for 2009 stage IIIA disease. Ten-year OS for 2023 stage IIIB2 (pelvic peritoneal involvement), previously 2009 stage IVB, was 49.4%, compared to 18.7% for 2009 stage IVB patients. Akaike information criterion, Bayesian information criterion, and Harrel's concordance index were used to evaluate OS prognostication of each staging system across all stages, with likelihood ratio favoring the 2023 system (p = 0.020). Conclusions: With FIGO's 2023 endometrial cancer anatomic and histologic staging system, stage migration is greatest in early-stage disease. New staging groups may offer more precise prognostication. These changes may affect future management.