Impact of FIGO 2023 Staging Criteria for Endometrial Cancer on Stage Migration: A Single Centre Cross-sectional Study

Introduction: The 2023 FIGO (International Federation of Gynaecology and Obstetrics) staging for endometrial cancer (EC) has introduced marked changes from the 2009 criteria. Histology, Lymphovascular Space Invasion (LVSI), and molecular features have been incorporated into the new classification system, leading to stage migration of Endometrial Cancer (EC), greatest in early-stage disease. Aim: To analyse the difference between the FIGO 2009 and FIGO 2023 classification systems for EC. Materials and Methods: This cross-sectional, observational study included EC cases reported in the Department of Pathology, College of Medicine and JNM Hospital, Kalyani, West Bengal, India, over a ten year period from April 2015 to April 2025. The study population comprised 51 cases of EC. Each case of EC was staged according to both the FIGO 2009 staging scheme and the FIGO 2023 system. Stage migration was assessed according to the 2023 FIGO staging scheme. McNemar’s test was used to test the significance of differences in Stage I and Stage II between the 2009 and 2023 classification systems. Confidence intervals (CI) and posthoc power were calculated. To determine agreement between the 2009 and 2023 schemes, Cohen’s kappa was calculated. All statistical analyses were performed using International Business Machines Statistical Package for the Social Sciences (IBM SPSS) Statistics version 30. Results: Stage distribution according to the 2009 FIGO scheme was 74.5% (n=38) for Stage I, 7.8% (n=4) for Stage II, 17.6% (n=9) for Stage III, and 0% for Stage IV, respectively; and according to the 2023 FIGO scheme it was 54.9% (n=28) Stage I, 29.4% (n=15) Stage II, 15.7% (n=8) Stage III, and 0% for Stage IV. Between the two schemes, in the 2023 staging system, Stage I distribution decreased from 74.5% (n=38) to 54.9% (n=28), whereas Stage II distribution increased from 7.8% (n=4) to 29.4% (n=15) and Stage III distribution decreased from 17.6% (n=9) to 15.7% (n=8). Based on the 2023 staging system, stage shifting occurred in 23.5% (n=12) of cases. Four cases were upstaged from IA to IIC and seven cases from IB to IIB. One case was downstaged from IIIA to IA. McNemar’s test showed a significant difference in Stage I proportion between the 2009 and 2023 schemes (p=0.004) and a significant increase in Stage II assignments with the 2023 scheme (p=0.0009). The CIs for Stage I and Stage II differences were 6.30% to 32.92% and -34.31% to -8.83%, respectively. Cohen’s kappa was 0.579. Post-hoc power calculation showed that the study had 84.45% power to detect the observed Stage I difference. Conclusion: FIGO 2023 significantly reduces Stage I EC and significantly increases Stage II EC due to modifications in its criteria, incorporating substantial LVSI, myometrial invasion, and aggressive histologies. As the sample size is small for drawing broad conclusions, collaboration across multiple centres is required to enhance the study’s statistical power and ensure more generalisable findings.