Objective To evaluate the influence of body mass index (BMI) on endometrial tumor pathology, stage and complication rate and to identify individual prognostic factors, such as BMI, in types I and II endometrial cancer.

Design Register study included all Danish women who underwent surgery for uterine cancer or atypical endometrial hyperplasia (International Classification of Diseases-10 codes D070, DC549) 2005 to 2012 (n = 6003).

Main Outcome Measures Impact of BMI on type I and II endometrial cancer survival.

Materials and Methods Danish Gynecological Cancer Database data on women with type I and II endometrial cancer were retrieved. Kaplan-Meier plot was used to illustrate differences in survival in relation to BMI. Log-rank test was used to demonstrate difference between the curves. Cox regression hazard model was used to estimate hazard ratios (HR) of the effect of BMI on overall survival.

Results Four thousand three hundred thirty women were included. Women with type I cancer had a significantly better overall survival compared with those with type II cancer. Low BMI was associated with increased mortality in type I (HR, 2.07; 95% confidence interval [CI], 1.20–3.55), whereas in type II both low (HR, 1.68; 95% CI, 1.03–2.74) and high BMI (BMI, 30–35: HR, 1.54; 95% CI, 1.01–2.26 and BMI >40: HR, 2.15; 95% CI, 1.12–4.11) were significantly associated with increased mortality.

Conclusion Abnormal BMI is associated with increased mortality in subtypes of endometrial cancer. Underweight was associated with increased overall mortality in both types I and II, whereas obesity only disclosed a significant impact on overall mortality in type II.