Objective: We propose a new staging system for stage I endometrial cancer and compare its performance to the 1988 and 2009 International Federation of Gynecology and Obstetrics (FIGO) systems.
Methods: We analyzed patients with 1988 FIGO stage I endometrial cancer from January 1993 to August 2011. Low-grade carcinoma consisted of endometrioid grade 1 to grade 2 lesions. High-grade carcinoma consisted of endometrioid grade 3 or nonendometrioid carcinomas (serous, clear cell, and carcinosarcoma). The proposed system is as follows:
IA. Low-grade carcinoma with less than half myometrial invasion
IA1: Negative nodes
IA2: No nodes removed
IB. High-grade carcinoma with no myometrial invasion
IB1: Negative nodes
IB2: No nodes removed
IC. Low-grade carcinoma with half or greater myometrial invasion
IC1: Negative nodes
IC2: No nodes removed
ID. High-grade carcinoma with any myometrial invasion
ID1: Negative nodes
ID2: No nodes removed
Results: Data from 1843 patients were analyzed. When patients were restaged with our proposed system, the 5-year overall survival significantly differed (P < 0.001): IA1, 96.7%; IA2, 92.2%; IB1, 92.2%; IB2, 76.4%; IC1, 83.9%; IC2, 78.6%; ID1, 81.1%; and ID2, 68.8%. The bootstrap-corrected concordance probability estimate for the proposed system was 0.627 (95% confidence interval, 0.590–0.664) and was superior to the concordance probability estimate of 0.530 (95% confidence interval, 0.516–0.544) for the 2009 FIGO system.
Conclusions: By incorporating histological subtype, grade, myometrial invasion, and whether lymph nodes were removed, our proposed system for stage I endometrial cancer has a superior predictive ability over the 2009 FIGO staging system and provides a novel binary grading system (low-grade including endometrioid grade 1–2 lesions; high-grade carcinoma consisting of endometrioid grade 3 carcinomas and nonendometrioid carcinomas).