Exogenous Hormone Use and Endometrial Cancer in U.S. Black Women.

Background: Although endometrial cancer risk differs among white and black women, few data on its associations with exogenous hormone use in the latter group are available. Studies have reported lower endometrial cancer risk among users of oral contraceptives (OCs), but higher risk among users of estrogen-only female menopausal hormones (FMHs). Evidence for the risk among estrogen plus progestin FMHs users is equivocal.
Methods: We followed 47,555 Black Women's Health Study participants with an intact uterus from 1995 through 2013. Data on exogenous hormone use, covariates, and endometrial cancer were obtained biennially. Self-reported incident cases of endometrial cancer were confirmed by medical records or cancer registries whenever possible. We estimated incidence rate ratios (IRRs) and 95% confidence intervals (CIs) using Cox proportional hazards regression.
Results: We observed 300 endometrial cancer cases during 689,546 person-years of follow-up. Compared with never use, ≥10 years' duration of OC use was associated with lower risk (multivariable IRR = 0.45, 95% CI, 0.27-0.74), but risk was higher among current users of estrogen-only (IRR = 3.78, 95% CI, 1.69-8.43) and estrogen plus progestin FMH (IRR = 1.55, 95% CI, 0.78-3.11). Risk was not increased among former users of estrogen-only (IRR = 0.87, 95% CI, 0.44-1.72) or estrogen plus progestin FMH (IRR = 0.63, 95% CI, 0.36-1.09).Conclusions: Current use of estrogen-only and estrogen plus progestin FMH was associated with increased risk of endometrial cancer. Risk appeared lower among former users of estrogen plus progestin FMH. Long-term OC use was associated with reduced risk.Impact: Our results are generally consistent with those among white women. Cancer Epidemiol Biomarkers Prev; 27(5); 558-65. ©2018 AACR. ©2018 American Association for Cancer Research.