Racial/Ethnic Differences in Ovarian Cancer Risk: Results from the Multiethnic Cohort Study.

BackgroundIncidence rates of epithelial ovarian cancer (EOC) vary across racial/ethnic groups, yet little is known about the impact of hormone-related EOC risk factors in non-Whites.MethodsAmong 91,625 female Multiethnic Cohort Study participants, 155 incident EOC cases were diagnosed in Whites, 93 in African Americans, 57 in Native Hawaiians, 161 in Japanese Americans, and 141 in Latinas. We used Cox proportional hazards regression models to estimate hazard ratios (HR) and 95% confidence intervals (CI) for associations between race/ethnicity and EOC risk and between hormone-related factors and EOC risk across racial/ethnic groups.ResultsCompared with Whites, African Americans and Japanese Americans had a lower multivariable-adjusted EOC risk; Native Hawaiians had a suggestive higher risk. Parity and oral contraceptive (OC) use were inversely associated with EOC risk (P int race/ethnicity ≥ 0.43); associations were strongest among Japanese Americans (e.g., ≥4 vs. 0 children; HR = 0.45; CI, 0.26-0.79). Age at natural menopause and postmenopausal hormone (PMH) use were not associated with EOC risk in the overall population, but were positively associated with risk in Latinas (e.g., ≥5 years vs. never PMH use; HR = 2.13; CI, 1.30-3.49).ConclusionsWe observed strong associations with EOC risk for parity and OC use in Japanese Americans and PMH use and age at natural menopause in Latinas. However, differences in EOC risk among racial/ethnic groups were not fully explained by established hormone-related risk factors.ImpactOur study indicates there are racial/ethnic differences in EOC risk and risk factors, and could help improve prevention strategies for non-White women.