Reproductive factors and risk of epithelial ovarian cancer: results from the Asia Cohort Consortium.

Background: There are scarce data on risk factors for epithelial ovarian cancer (EOC) in Asian populations. Our goal was to advance knowledge on reproductive -related risk factors for EOC in a large population of Asian women.

Methods: This study used pooled individual data from baseline questionnaires in 11 prospective cohorts (baseline years, 1958-2015) in the Asia Cohort Consortium. A Cox proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for age, parity and cohort.

Results: After a mean = 17.0 years (SD = 6.3) of follow-up, 674 incident invasive EOC cases were identified among 325,626 women. In multivariable adjusted models we observed an inverse association with parity (5+ children vs. 0, HR = 0.44, 95% CI = 0.28-0.68, Ptrend < 0.001), and a positive association with increasing menopausal age (55+ years vs. <45, HR = 1.77, 95% CI = 1.05-3.01, Ptrend = 0.02) for risk of all EOC.

Conclusions: In this large study of Asian women we identified an inverse association with parity and a positive association with higher menopausal age in relation to EOC risk. Further work is needed to understand EOC risk factors for rare histologic subtypes that occur more frequently in Asian populations.