Race Differences in the Associations between Menstrual Cycle Characteristics and Epithelial Ovarian Cancer

Background: Menstrual cycle characteristics-including age at menarche and cycle length- have been associated with ovarian cancer risk in White women. However, the associations between menstrual cycle characteristics and ovarian cancer risk among Black women have been sparsely studied. Methods: Using the Ovarian Cancer in Women of African Ancestry (OCWAA) Consortium that includes 1,024 Black and 2,910 White women diagnosed with epithelial ovarian cancer (EOC) and 2,325 Black and 7,549 White matched controls, we investigated associations between menstrual cycle characteristics (age at menarche, age at menstrual regularity, cycle length, and ever missing three periods) and EOC risk by race and menopausal status. Multivariable logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI). Results: Black women were more likely to be <11 years at menarche than White women (controls: 9.9% vs. 6.0%). Compared with ≥15 years at menarche, <11 years was associated with increased EOC risk for White (OR ¼ 1.25; 95% CI, 0.99-1.57) but not Black women (OR ¼ 1.10; 95% CI, 0.80-1.55). Among White women only, the association was greater for premenopausal (OR ¼ 2.20; 95% CI, 1.31-3.68) than postmenopausal women (OR ¼ 1.06; 95% CI, 0.82-1.38). Irregular cycle length was inversely associated with risk for White (OR ¼ 0.78; 95% CI, 0.62-0.99) but not Black women (OR ¼ 1.06; 95% CI, 0.68-1.66). Conclusions: Earlier age at menarche and cycle irregularity are associated with increased EOC risk for White but not Black women. Impact: Associations between menstrual cycle characteristics and EOC risk were not uniform by race.