Risk factors for endometrial cancer in U.S. black women

Abstract

Black women have higher incidence rates of aggressive subtypes of endometrial cancer and worse survival rates compared with white women. The overall incidence rate has been increasing in black women and, accounting for their higher prevalence of hysterectomy, may be higher than in white women. Exposures related to obesity and metabolic disorders, reproductive factors, and use of exogenous hormones have been associated with endometrial cancer risk in prior studies. However, because these studies have primarily included white women, little is known about these associations in black women. We therefore examined associations of endometrial cancer with previously identified risk factors in 47,555 participants in the Black Women’s Health Study, a prospective cohort of U.S. black women. Study 1 focused on anthropometric and metabolic factors. After adjustment for age at menarche, parity, menopausal status, smoking, and use of oral contraceptives, estrogen-only female menopausal hormones (FMH), and estrogen plus progestin FMH, self-reported body mass index (BMI), BMI at age 18, greater weight gain since age 18, and diagnosis of diabetes were positively associated with endometrial cancer risk. Self-reported diagnosis of hypercholesterolemia and hypertension were not independently associated. In study 2, we examined associations with reproductive factors. Endometrial cancer incidence was higher among women with early age at menarche, a history of infertility, a greater number of lifetime menstrual cycles, and diagnosis of polycystic ovary syndrome. Parity and early age at first birth were associated with lower risk, while a greater number of births and breastfeeding were not associated with risk. Positive associations with late age at menarche among premenopausal women and longer duration of breastfeeding among obese women require confirmation in other studies. In study 3, we examined the associations of endometrial cancer with exogenous hormone use. The inverse association with oral contraceptive use was primarily among women who used oral contraceptives for ≥5 years. Incidence was higher among current users of estrogen-only and estrogen plus progestin FMH, and ever users of progestin only FMH. Lower risk was observed among former users of estrogen plus progestin FMH.