Comparative Prognostic Evaluation of the Revised International Federation of Gynecology and Obstetrics 2023 and 2009 Staging Systems in Early Endometrial Cancer

Background/Objectives: We comparatively evaluated the prognostic performance of the 2009 and 2023 International Federation of Gynecology and Obstetrics (FIGO) staging systems for early-stage endometrial cancer based on histological subtype stratification. Methods: A retrospective cohort of 472 patients with FIGO 2009 stage I–II between 2004 and 2019 was analyzed. Patients were restaged using both systems. Overall survival (OS) and recurrence-free survival (RFS) were determined according to histopathological aggressiveness. Kaplan–Meier survival analysis with log-rank testing compared the performance of the systems. Cox proportional hazards regression identified independent prognostic factors. A hypothetical modification of the FIGO 2023 system was evaluated for aggressive subtypes. Results: In all, 388 patients had nonaggressive histology, and 84 patients had aggressive histology. For cases of nonaggressive histology, FIGO 2023 demonstrated superior prognostic discrimination for OS and RFS (p < 0.05), whereas FIGO 2009 showed significant stratification for OS (p < 0.001) but not RFS (p = 0.149). For cases of aggressive histology, FIGO 2009 showed significant stratification for RFS (p = 0.017) but not OS (p = 0.31), whereas FIGO 2023 showed no significant stratification for either endpoint. The hypothetical modification of the FIGO 2023 staging system showed significantly improved discrimination for RFS (p = 0.019) but not OS. Multivariate analysis identified age and lymphovascular space invasion as independent prognostic factors in nonaggressive cancers, whereas cervical stromal involvement was significant in aggressive subtypes. Conclusions: The prognostic utility of the FIGO staging system is histology dependent. Although FIGO 2023 offers enhanced risk stratification for nonaggressive endometrial cancers, its discriminatory power for aggressive subtypes remains limited, indicating the need for histology-specific refinements of future staging frameworks.