Abstract B42: Intrauterine device use and ovarian cancer risk
Authors: Sasamoto Naoko , Yang Jiaxi , Babic Ana , Vitonis Allison F. , Cramer Daniel W. , Titus Linda J. , Tworoger Shelley S. , Terry Kathryn L. 
Published: September 2020

Abstract
Background: An estimated 38 million American women currently use contraception, a critical key to women’s health with respect to preventing unwanted pregnancies and reducing maternal morbidity and mortality. Additionally, oral contraceptives (OC) reduce ovarian cancer risk by an estimated 15-30% and are credited with the decreasing ovarian cancer incidence over recent decades. However, contraceptive patterns are changing, with OC use decreasing in favor of intrauterine devices (IUDs). Studies regarding IUD use and ovarian cancer risk are inconsistent, with most reporting decrease in risk or no association. Differences between these studies could be attributable to IUD type, duration of use, age at first use, or type of ovarian cancer. Here we examined the association between IUD use, including duration, type, and timing of use, and ovarian cancer risk using three population-based studies.
Methods: In the New England Case-Control Study, a population-based study enrolling participants in New Hampshire and Eastern Massachusetts from 1992 to 2008, 2,323 ovarian cancer cases and 2,339 frequency-matched population-based controls were included in the analysis. Information on IUD use was collected using questionnaire data at time of enrollment. Unconditional logistic regression adjusted for potential confounders including age, body mass index, smoking status, age at menarche, parity, OC use, tubal ligation, genital powder use, endometriosis, family history of ovarian cancer, center, and study phase was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs). In the Nurses’ Health Studies (NHS/NHSII), prospective cohort studies established in 1976 and 1989 enrolling 121,700 and 116,429 registered nurses residing in 11 and 14 US states, 1,761 ovarian cancer cases were confirmed through 2015. Information on IUD use was collected in biennial questionnaires from 1976 to 1982. Cox regression adjusted for potential confounders listed above was used to calculate the hazard ratios (HRs) and 95% CIs. NHS and NHSII cohorts were pooled and models were adjusted for cohort. Polytomous logistic regression was used to evaluate the association by histotypes.
Results: Overall, IUD use was not associated with ovarian cancer risk (OR=0.99, 95%CI: 0.83-1.17 in NEC; HR=0.89, 95%CI: 0.69-1.15 in NHS/NHSII). While histotype specific associations were not significantly different, IUD use was suggestively associated with increased risk of serous borderline tumors (OR=1.42, 95% CI: 1.00-2.02 in NEC). There was no significant difference by IUD type, duration, or age at first IUD use. The association between IUD use and ovarian cancer risk did not differ when stratified by parity.
Conclusion: IUD use was not significantly associated with ovarian cancer risk, although the current study was limited by small sample size to investigate the association between detailed IUD use and risk. Larger studies are warranted to further investigate the association between patterns of IUD use and ovarian cancer risk.
Citation Format: Naoko Sasamoto, Jiaxi Yang, Ana Babic, Allison F. Vitonis, Daniel W. Cramer, Linda J. Titus, Shelley S. Tworoger, Kathryn L. Terry. Intrauterine device use and ovarian cancer risk [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 B42.