Objectives High-risk histology including UPSC, CC, and high-grade (G3) endometrioid adenocarcinoma (EAC) have a worse prognosis compared to G1-2 EAC. It is unknown whether G3EAC outcomes are more similar to UPSC/CC or to G1-2 EAC. The purpose of this study was to compare overall survival (OS) among UPSC, CC, and G1-3 EAC, for International Federation of Gynecology and Obstetrics stages I to III.

Methods The National Cancer Data Base was queried for patients diagnosed with International Federation of Gynecology and Obstetrics (1988 classification) Stage I-III UPSC, CC, and EAC from 1998 to 2012 who underwent surgery as definitive treatment. Patients with unknown grade/stage, nonsurgical primary therapy, other histologies, and less than 30-day follow-up were excluded. Overall survival was calculated using the Kaplan-Meier product-limit method and compared using log-rank tests.

Results 219,934 patients met our inclusion criteria. For patients with stage I disease (n = 174,361), 5-year OS was for 92.4% for G1EAC, 87.8% for G2EAC, 77.5% for G3EAC, 74.9% for CC, and 74.6% for UPSC. For stage II patients (n = 17,361), 5-year OS was 86.7% for G1EAC, 80.2% for G2EAC, 62.7% for G3EAC, 64.3% for CC, and 56.7% for UPSC. For stage III patients (n = 28,212), 5-year OS was 79.7% for G1EAC, 68.9% for G2EAC, 49.6% for G3EAC, 40.2% for CC, and 35.7% for UPSC (P <0.0001). On multivariate analysis, black race, age 60 years and older, higher stage, higher grade, high-risk histologies, receiving chemotherapy, and higher comorbidity scores were all significantly (P < 0.0001) predictive of death while receiving radiation therapy was protective (hazards ratio, 0.7; 95% confidence interval, 2.6–2.9).

Conclusions The results suggest that G3 EAC has a slightly more favorable survival than UPSC and CC but predictably does poorer than G1-2 EAC. Further research is warranted to determine if G3 EAC should be reclassified as a type II cancer.