Validation of 2023 FIGO Stage IA1-IIIC2 Endometrial Carcinoma: A Retrospective Analysis of Two Tertiary Centers in South Korea and Taiwan

Purpose As understanding of the molecular pathogenesis of endometrial carcinoma (EC) advanced, the International Federation of Gynecology and Obstetrics (FIGO) staging system was revised in 2023. This study compared EC survival outcomes using the 2009 and 2023 FIGO staging systems. Materials and Methods We retrospectively analyzed 3,029 patients diagnosed with 2009 FIGO stage I-III EC between 1985 and 2022 in South Korea, and between 2020 and 2022 in Taiwan. All patients were reclassified using the 2023 FIGO staging, and survival and risk factors were examined under both systems. Results Transitioning from the 2009 to 2023 FIGO resulted in 549 patients (18.0%) being upstaged and their survival curves being diversified, indicating significant prognostic value of the 2023 FIGO. Re-classification using the 2023 FIGO upstaged the 2009 FIGO stage IA high-risk ECs, allowing more intensive treatment and potentially improving survival outcomes. The most significant changes occurred in the 2009 FIGO stages IA, IB, and IIIA ECs: upstaging in 16.5%, 49.0%, and 2.0% of IA, IB, and IIIA tumors, respectively, and downstaging 0.3% and 40.8% of IB and IIIA tumors, respectively. The risk factors for poor survival included old age (≥ 60 years), menopause, diabetes, substantial lymphovascular space invasion, aberrant p53 expression, and some aggressive histological types (carcinosarcoma, undifferentiated carcinoma, mesonephric-like adenocarcinoma, and neuroendocrine carcinoma). Conclusion The 2023 FIGO staging provides more refined stratification of early-stage EC than the 2009 version. Thus, the 2023 FIGO may more accurately guide prognosis and therapeutic decision-making.