Abstract B32: Are ovarian cancer risk factors different for women with endometriosis?

Abstract Background: Endometriosis is a common gynecologic disorder that affects approximately 10% of women of reproductive age. It is also a well-established risk factor for ovarian cancer. Whether hormonal-related and other risk factors for ovarian cancer (e.g., parity, oral contraceptive use) are the same for women with and without endometriosis is currently unknown. Methods: We pooled questionnaire information from 10 population-based case-control studies participating in the Ovarian Cancer Association Consortium (OCAC). Data from 8,172 women with invasive epithelial ovarian cancer and 12,464 controls were included in our analysis. Associations of body mass index (BMI), parity, oral contraceptive use, breastfeeding, menopausal hormone therapy use, first-degree family history of ovarian cancer, tubal ligation, and hysterectomy with risk of ovarian cancer were stratified by history of endometriosis and analyzed using logistic regression. All models were conditioned on age, race/ethnicity, education, and OCAC study site. We fit an endometriosis interaction term for each risk factor to evaluate statistical interactions. Results: Among women with no history of endometriosis, those who had hysterectomies showed a 12% increased risk of ovarian cancer compared to those with intact uteri (OR=1.12, 95% CI 1.01-1.24); an increased risk was not observed among women with endometriosis (OR=0.74, 95% CI 0.53-1.05; p-interaction=0.009). Use of estrogen-progestin hormone therapy was associated with decreased risk ovarian cancer for women with histories of endometriosis (OR=0.69, 95% CI 0.47-1.02), but not for those without endometriosis (OR=0.96, 95% CI 0.87-1.07; p-interaction=0.02). We did not observe any significant statistical interactions for the other risk factors considered, and no interactions were significant after consideration of multiple comparisons. Conclusions: The associations of hysterectomy and menopausal estrogen-progestin hormone therapy use with risk of ovarian cancer seemed to differ by endometriosis status, suggesting interactions that may need to be considered in ovarian cancer risk profiling strategies. Future investigations into the biology underlying these interactions would be relevant. Citation Format: Aruna Muthukumar, Lilah Khoja, Penelope M. Webb, Harvey Risch, Jennifer Doherty, Holly Harris, Marc Goodman, Roberta Ness, Francesmary Modugno, Susanne K. Kjaer, Allan Jensen, Joellen Schildkraut, Andrew Berchuck, Kathryn L. Terry, Daniel Cramer, Linda J. Titus, Hoda Anton-Culver, Argyrios Ziogas, Anna H. Wu, Malcolm C. Pike, Celeste L. Pearce, Alice W. Lee. Are ovarian cancer risk factors different for women with endometriosis? [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B32.