Validation of the 2023 FIGO staging system and its concordance with the JSGO guidelines in endometrial cancer: A multi-institutional retrospective study in Japan.

Aim: To validate the prognostic accuracy of the 2023 FIGO staging system and assess its alignment with the Japan Society of Gynecologic Oncology (JSGO) guidelines for endometrial cancer treatment.

Methods: This retrospective cohort study included 1207 patients with endometrial cancer treated at four academic hospitals in Kanagawa, Japan, between 2018 and 2022. Patients were reclassified according to the FIGO 2023 system and the JSGO recurrence risk categories. Primary endpoints included stage migration, recurrence risk (RR), overall survival (OS), and concordance between the two classification systems.

Results: Under FIGO 2023, the stage distribution was: I, 741 (61.4%); II, 203 (16.8%); III, 149 (12.3%); and IV, 114 (9.4%), with stage migration observed in 36.3% of cases. The FIGO 2023 system provided clearer stratification of 3-year RR than FIGO 2009, with the RR gap widening from 80.0% to 90.1%. Sixteen patients (3.5%) with stage IA3 were classified as high risk by JSGO criteria, while 14.4% of patients considered high risk by JSGO were downstaged under FIGO 2023. Additionally, 46 patients (19.6%) with FIGO stage IA were reclassified as intermediate risk owing to focal lymphovascular space invasion (LVSI). Substantial LVSI was significantly associated with recurrence and poor prognosis (3-year OS rates: none 94.3%, focal 89.9%, and substantial 40.7%; p < 0.05). Molecular testing was limited: p53 in 30.2%, MSI in 5.9%, and POLE was not available.

Conclusions: FIGO 2023 improves prognostic precision. Incorporating LVSI extent and molecular data may refine JSGO classifications and support more individualized adjuvant therapy strategies.