Abstract 2217: Associations between intrauterine device use and ovarian cancer risk among 11 population-based case-control studies

Abstract Background: Intrauterine device (IUD) use has increased while oral contraceptive (OC) use has decreased among premenopausal women. It is unknown whether IUDs offer protection against epithelial ovarian cancer (EOC), similar to OCs, or may increase risk. Therefore, we examined the association between IUD use and EOC risk. Methods: Information on contraception use was obtained through questionnaires from 11 studies participating in the Ovarian Cancer Association Consortium and African-American Cancer Epidemiology Study. Study-specific odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional multivariable logistic regression, and heterogeneity between studies was assessed using Cochran Q and I2 statistics. There was no evidence of heterogeneity, thus data were pooled. We assessed potential effect modification by decade of birth, race, parity, and personal history of endometriosis by reporting stratum-specific estimates and tested for multiplicative interaction by comparing models with and without interaction terms via likelihood ratio test. Polytomous logistic regression was used to estimate histotype-specific associations. Results: Results were pooled for 11, 033 EOC cases and 13, 358 controls. There were 2, 656 (19. 9%) IUD users (mostly non-hormonal) and 8, 923 (66. 8%) OC users among controls compared to 1, 933 (17. 5%) IUD users and 6, 318 (57. 3%) OC users among cases. IUD use was associated with lower risk of endometrioid (OR: 0. 73, 95% CI: 0. 62-0. 86) and clear cell (OR: 0. 63, 95% CI: 0. 48-0. 80), but not high-grade serous subtypes (OR: 1. 05, 95% CI: 0. 98-1. 14), with significant heterogeneity by histotype (p=0. 0006). Among studies that collected data on IUD type, we observed a non-significant inverse association between hormonal IUD use and EOC (OR: 0. 72, 95% CI: 0. 51-1. 03) ; however, only 51 cases reported hormonal IUD use. Among those who used both IUD and OCs, there was no association with the order of contraception use and EOC. There were no major differences in the associations of age at first use, duration of use, or time since last use and EOC risk. Among parous women, IUD use before first pregnancy was associated with a non-significant reduced odds of EOC (OR: 0. 82, 95% CI: 0. 65-1. 04). We also observed a statistically significant interaction between IUD use and endometriosis with reduced odds of EOC associated with IUD use among women with endometriosis (OR: 0. 77, 95% CI: 0. 60-0. 98) but not those without endometriosis (OR: 0. 96, 95% CI: 0. 90-1. 03, p-interaction=0. 05). Discussion: IUD use was associated with lower clear cell and endometrioid EOC risk and may be most protective among women with endometriosis. Future research should include cohorts of women with a higher prevalence of hormonal IUD use to determine the impact of changing contraceptive trends on ovarian cancer burden and identifying preventive strategies for women at high risk. Citation Format: Jennifer M. Mongiovi, Ana Babic, Naoko Sasamoto, Lauren Peres, Holly Harris, Mollie E. Barnard, Shelley S. Tworoger, Anita Koushik, Joellen M. Schildkraut, Jennifer A. Doherty, Kathryn L. Terry, the Ovarian Cancer Association Consortium Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2217.