Effect of the new FIGO 2023 staging system on stage distribution and adjuvant therapies in endometrial cancer: A retrospective cohort study

Objective: The 2023 update of the International Federation of Gynecology and Obstetrics (FIGO) staging system introduced significant changes in the classification of endometrial cancer by incorporating key pathological and molecular features. This study aimed to evaluate the impact of the revised FIGO 2023 staging system on stage distribution and adjuvant treatment decisions in patients undergoing surgical management of this malignancy. Materials and Methods: This retrospective study included 220 patients who underwent surgical staging for endometrial cancer between January 2018 and December 2025. All patients were initially staged using the FIGO 2009 classification. Cases were subsequently reclassified according to the FIGO 2023 staging criteria, using the algorithm proposed for settings in which routine molecular classification is unavailable. The McNemar test was used to compare stage categories between the two staging systems, and the Wilcoxon signed-rank test was applied to evaluate the impact of stage migration on adjuvant treatment recommendations. Results: Stage migration occurred in 12.7% of patients (28/220) following the application of the FIGO 2023 criteria, predominantly due to upstaging. The most common factor associated with stage reclassification was substantial lymphovascular space invasion (LVSI). The proportion of patients managed with observation alone significantly decreased from 44.5% to 32.7% (p<0.001), while the use of pelvic radiotherapy increased from 19.1% to 28.2% (p=0.004). Similarly, the proportion of patients receiving combined chemoradiotherapy significantly increased from 11.8% to 17.3% (p=0.012). Conclusion: The implementation of the FIGO 2023 staging system has resulted in clinically meaningful stage migration and significantly impacted adjuvant treatment strategies. In particular, the recognition of substantial LVSI as a defining feature of stage IIC disease has led to more intensive adjuvant therapy in a subset of patients previously categorized as low risk.