Purpose: To construct a new clinical staging system including the number of lymph node metastases to supplement the International Federation of Gynecology and Obstetrics (FIGO) staging for the prognosis of endometrial carcinoma patients.
Methods: This cohort study retrieved the data of 28,824 patients confirmed as endometrial carcinoma between 2010 and 2015 in the surveillance, epidemiology, and end results (SEER) database. COX risk proportional model was established to evaluate the association between FIGO staging with the all-cause mortality of endometrial carcinoma. The diagnostic value of FIGO staging and the new staging for the mortality of patients were evaluated by receiver operator characteristic curve (ROC). Hazard ratio (HR) and 95% confidence interval (CI) were effect size.
Results: The 5-year survival rate of all participants was 77.21%. The median follow-up time was 60.00 (60.00,60.00) months. Patients at FIGO staging IB (HR=1.75, 95% CI: 1.62– 1.90), FIGO staging II (HR=2.22, 95% CI: 2.00– 2.47), FIGO staging IIIA (HR=2.74, 95% CI: 2.43– 3.09), FIGO staging IIIB (HR=4.07, 95% CI: 3.48– 4.76), FIGO staging IIIC1 (HR=3.84, 95% CI: 3.52– 4.20), FIGO staging IIIC2 (HR=4.52, 95% CI: 4.09– 4.99), FIGO staging IVA (HR=5.56, 95% CI: 4.58– 6.74), and FIGO staging IVB (HR=7.62, 95% CI: 6.94– 8.36) were associated with increased risk of all-cause mortality of endometrial carcinoma patients. After adding positive lymph nodes as another covariate in Model 3, the effect on of FIGO staging survival was reduced when the FIGO staging was higher than stage III/IV. The C-index of the new staging 0.781 (95% CI: 0.774– 0.787) was higher than FIGO staging 0.776 (95% CI: 0.770– 0.783).
Conclusion: Our new staging using the number of positive lymph nodes supplement to the FIGO staging was superior than the FIGO staging for predicting the prognosis of endometrial cancer patients, which might help more accurately identify endometrial carcinoma patients who were at high risk of mortality and offer timely treatments in these patients.

Keywords: positive lymph nodes, FIGO staging, endometrial cancer, prediction