Obesity in relation to endometrial cancer risk and disease characteristics in the Women's Health Initiative

Objective: Obesity increases endometrial cancer risk, yet its impact on disease stage and grade is unclear. We prospectively examined the effects of body mass index (BMI) and waist-to-hip ratio (WHR) on incidence, stage, and grade of endometrial cancer. Methods: We studied 86 937 postmenopausal women enrolled in the Women's Health Initiative. Height, weight, and waist and hip circumference were measured at baseline. Endometrial cancer cases were adjudicated by trained physicians and pathology reports were used to determine stage and grade. Cox proportional hazards models generated hazard ratios (HR) for associations between BMI and WHR and risk of endometrial cancer. Logistic regression was used to evaluate associations between BMI and WHR and disease stage and grade. Results: During a mean 7.8 (standard deviation 1.6) years of follow-up, 806 women were diagnosed with endometrial cancer. Although incidence was higher among Whites, stage and grade were similar between Whites and Blacks. Elevated BMI (HR 1.76, 95% confidence interval [CI] 1.41-2.19) and WHR (HR 1.33, 95% CI 1.04-1.70) increased endometrial cancer risk when comparing women in the highest and lowest categories. No associations were observed between BMI or WHR and disease stage or grade. Conclusions: Obesity increases endometrial cancer risk independent of other factors but is not associated with stage or grade of disease. These findings support and validate previous reports. Future research should evaluate the impact of obesity on racial disparities in endometrial cancer survival.