Background: Long and irregular menstrual cycles, a hallmark of polycystic ovary syndrome (PCOS), have been associated with higher androgen and lower sex hormone binding globulin levels (SHBG) and this altered hormonal environment may increase the risk of specific histologic subtypes of ovarian cancer.

Methods: We investigated the association between menstrual cycle characteristics and PCOS among 2071 women with epithelial ovarian cancer and 2100 controls in the New England Case-Control Study (1992-2008). Women self-reported menstrual cycle irregularity, menstrual cycle length, and previous diagnosis of PCOS. We used unconditional logistic regression models to calculate odds ratios (OR) and 95% confidence intervals (95% CIs) for ovarian cancer risk overall, and polytomous logistic regression to evaluate whether the associations differed across histologic subtypes.

Results: Overall, we observed no difference in ovarian cancer risk between women who reported periods that were never regular and women who did not report menstrual cycle irregularity (multivariable OR=0.87; 95% CI=0.69-1.10). A similar association was observed for those reporting an average menstrual cycle length of greater than 35 days with a multivariable OR of 0.87 (95% CI=0.47-1.60). In addition, no association was observed with self-reported PCOS and ovarian cancer (multivariable OR=0.96; 95% CI=0.60-1.54). When we examined the associations by histologic subtype, we observed significant differences in the association with menstrual cycle irregularity as the exposure (pheterogeneity=0.007) but not for cycle length >35 days or self-reported PCOS. Menstrual cycle irregularity was protective for serous invasive tumors (OR=0.66; 95% CI=0.47-0.91) but was associated with a non-significant increase in risk of serous borderline tumors (OR=1.32; 95% CI=0.86-2.03).

Conclusions: Our results suggest that menstrual cycle characteristics may have influences on ovarian cancer risk that vary by histologic subtype. Future research in a large collaborative consortium may help clarify these associations.

Citation Format: Holly R. Harris, Linda J. Titus, Daniel W. Cramer, Kathryn L. Terry. Menstrual cycle characteristics, PCOS, and ovarian cancer risk. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B37.