Abstract B41: Racial/ethnic disparities in epithelial ovarian cancer and its risk factors: The Multiethnic Cohort Study
Authors: Sarink Danja , Park Song Yi , Le Marchand Loic , White Kami , Hernandez Brenda , Wilkens Lynne , Setiawan V. Wendy , Wu Anna , Merritt Melissa A. 
Published: September 2020

Abstract
Background: Age-adjusted incidence rates of epithelial ovarian cancer (EOC) are highest rates in White and Hispanic women, and lower in African American and Asian/Pacific Islander women. We investigated the extent to which reproductive and lifestyle factors explain racial/ethnic differences in EOC risk among White, African American, Native Hawaiian, Japanese American, and Hispanic women in the Multiethnic Cohort (MEC) Study.
Methods: The study included 91,682 participants who completed a baseline questionnaire on hormone-related and other lifestyle factors. Incident invasive EOC cases were identified from tumor registries. We used Cox proportional hazards regression models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between (1) race/ethnicity and EOC risk and (2) hormone-related factors and EOC risk across racial/ethnic groups. Exposures included parity, ages at first birth, menarche, and natural menopause, menopausal status, exogenous hormone use, and body mass index. Models were adjusted for age, menopausal status, parity, and oral contraceptive (OC) use.
Results: During a median of 20 years of follow-up, 155 EOC cases occurred among Whites, 93 among African Americans, 57 among Native Hawaiians, 161 among Japanese Americans, and 141 among Latinas. Compared to Whites, African Americans and Japanese Americans had a lower EOC risk (HR 0.74 [CI 0.57-0.97] and HR 0.79 [CI 0.63-0.99], respectively) while Native Hawaiians had a suggestive higher risk (HR 1.36 [CI 0.99-1.85]). EOC risk in Latinas did not differ from that in Whites (HR 0.97 [CI 0.76-1.22]). Parity and OC use were significantly inversely associated with EOC risk in the full population. These risk patterns were observed across race/ethnicity (pint ≥0.43), with the strongest inverse associations among Japanese Americans (≥4 vs. 0 children, HR 0.45 [CI 0.26-0.79], ptrend &lt;0.01; ≥5 years vs. never OC use, HR 0.35 [CI 0.16-0.78]). Though there was no association in the full population, age at natural menopause (≥55 vs. ≤45 years, HR 2.60 [CI 1.24-5.42]) and postmenopausal hormone use (≥5 years vs. never, HR 2.13 [CI 1.30-3.49]) were positively associated with EOC risk among Latinas. There were no significant associations among White, African American, or Native Hawaiian women for any of the risk factors tested.
Conclusion: Our results suggest that differences in risk among ethnic groups were not fully explained by established risk factors and differences in risk remained, with increased risk observed in Native Hawaiians and lower risk in Latinas and Japanese Americans, compared to Whites. EOC is a rare disease, and case numbers limited our ability to further explore associations across the racial/ethnic groups in the MEC study.
Citation Format: Danja Sarink, Song Yi Park, Loic Le Marchand, Kami White, Brenda Hernandez, Lynne Wilkens, V. Wendy Setiawan, Anna Wu, Melissa A. Merritt. Racial/ethnic disparities in epithelial ovarian cancer and its risk factors: The Multiethnic Cohort Study [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 B41.