Objective Two distinct types of endometrial carcinoma (EC) with different etiology, tumor characteristics, and prognosis are recognized. We investigated if the prognostic impact of comorbidity varies between these 2 types of EC. Furthermore, we studied if the recently developed ovarian cancer comorbidity index (OCCI) is useful for prediction of survival in EC.

Materials and Methods This nationwide register-based cohort study was based on data from 6487 EC patients diagnosed in Denmark between 2005 and 2015. Patients were assigned a comorbidity index score according to the Charlson comorbidity index (CCI) and the OCCI. Kaplan-Meier survival statistics and adjusted multivariate Cox regression analyses were used to investigate the differential association between comorbidity and overall survival in types I and II EC.

Results The distribution of comorbidities varied between the 2 EC types. A consistent association between increasing levels of comorbidity and poorer survival was observed for both types. Cox regression analyses revealed a significant interaction between cancer stage and comorbidity indicating that the impact of comorbidity varied with stage. In contrast, the interaction between comorbidity and EC type was not significant. Both the CCI and the OCCI were useful measurements of comorbidity, but the CCI was the strongest predictor in this patient population.

Conclusions Comorbidity is an important prognostic factor in type I as well as in type II EC although the overall prognosis differs significantly between the 2 types of EC. The prognostic impact of comorbidity varies with stage but not with type of EC.