Abstract 641: Oral contraceptive use and risk of highly fatal ovarian cancer: Evidence from the Ovarian Cancer Association Consortium

Objectives: While oral contraceptives (OC) use is associated with lower risk of ovarian cancer compared to non-users, its role in the etiology of aggressive and highly fatal disease has not been determined. Thus, we utilized data from the Ovarian Cancer Association Consortium (OCAC) to evaluate the association between pre-diagnostic OC use and highly fatal ovarian cancer. Methods: Data were pooled from 20 case-control studies participating in OCAC to examine the association between oral contraceptive use and risk of highly fatal ovarian cancer; defined as dying within 12 or 18-months of diagnosis. Controls were frequency matched to cases (4:1) on five-year age categories, race, and study site. The study samples included 579 patients who died within 12 months of their diagnosis, matched to 2279 controls as well as 1294 patients who died within 18-months, matched to 5095 controls. Analyses were performed using unconditional logistic regression, and separate models were run for any use of OC and duration of OC use per five year increase. Race, education, prior hysterectomy or tubal ligation, parity, age at menarche, menopausal status, and smoking status were assessed as potential confounders of the association. Results: After adjusting for age, site, and parity, any OC use was associated with a 46% reduction in the odds of death within 12-months after adjusting for age, site, and parity (OR=0.54, 95% CI: 0.43-0.68). There was also a significant trend of decreased odds with increased duration of OC use. Among those who used OC for over 10 years, a 66% reduction in the odds of death within 12-months was observed (OR=0.34, 95% CI: 0.23-0.49) while there was no significant benefit from use of OC for 1 year or less (OR=0.83, 95% CI: 0.60-1.14). Similar trends were observed among those who died within 18-months, although OC use appeared to be more protective among highly fatal cases. Use of OC was most protective for endometrioid subtypes among both those who died within 12-months (OR=0.43, 95% CI: 0.20-0.93) and 18-months (OR=0.39, 95% CI: 0.23-0.65). Conclusions: To our knowledge, this is the first large, multi-center study to investigate the association between OC use and risk of highly fatal ovarian cancer. These results are in line with current evidence that has demonstrated a substantial decrease in risk of ovarian cancer with OC use for five or more years. Future research should aim at understanding the mechanisms behind this association and identifying specific subpopulations that may benefit most from this chemopreventive strategy. Citation Format: Jennifer M. Mongiovi, Janine M. Joseph, Albina N. Minlikeeva, Ahmad AlSulimani, Hani Almohanna, Kirsten B. Moysich. Oral contraceptive use and risk of highly fatal ovarian cancer: Evidence from the Ovarian Cancer Association Consortium [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 641.