Prognostic comparison of the FIGO 2009 and 2023 endometrial cancer staging systems: a large, single-institution...

The International Federation of Gynecology and Obstetrics 2023 endometrial cancer staging system includes 21 sub-stages and proposes a shift from pure anatomical staging to an approach incorporating histology, grade, lymphovascular invasion, and molecular classification. We sought to evaluate the overall survival prognostic ability of the International Federation of Gynecology and Obstetrics 2023 endometrial cancer staging system compared with the International Federation of Gynecology and Obstetrics 2009 system.

We collected clinicopathologic characteristics, molecular profiling results, and survival outcomes for all patients with a new diagnosis of endometrial cancer treated at our institution between 2016 and 2020. All cases underwent pathology review by a gynecologic pathologist at our institution. An International Federation of Gynecology and Obstetrics 2009 and 2023 stage was assigned. We applied R²ϵ statistics based on an isotonic proportional hazards model to compare prognostic ability between the 2 staging systems.

Of 2067 patients with endometrial cancer, 952 (46%) underwent tumor molecular profiling. When comparing International Federation of Gynecology and Obstetrics 2009 and 2023 staging, 538 (26.0%) patients were upstaged and 100 (4.8%) were downstaged in the 2023 system. Five-year overall survival estimates were similar across most stages between the 2 staging systems, with some exceptions: the International Federation of Gynecology and Obstetrics 2023 IA3 sub-stage demonstrated improved outcomes (100% vs 70.3% for International Federation of Gynecology and Obstetrics 2009 IIIA) and the IICm_p53abn group had poorer prognosis (73% vs 86.8% for International Federation of Gynecology and Obstetrics 2009 II). Using isotonic proportional hazards regression models, the 2023 model slightly numerically outperformed the 2009 model for overall survival (R²ϵ 0.546 vs 0.415); however, adjusted 95% confidence intervals were under-developed.

Using a real-world, large, well-annotated cohort of patients with endometrial cancer with expert pathology review, we were able to calculate 5-year progression-free and overall survival rates for each sub-stage. The International Federation of Gynecology and Obstetrics 2023 model demonstrated slightly improved prognostic discrimination compared with the International Federation of Gynecology and Obstetrics 2009 model; however, small patient numbers in each sub-stage and concerns regarding over-fitting limit this analysis.