Parity and Oral Contraceptive Use in Relation to Ovarian Cancer Risk in Older Women.

Background: Several studies have suggested that the ovarian cancer risk reductions associated with parity and oral contraceptive use are weaker in postmenopausal than premenopausal women, yet little is known about the persistence of these reductions as women age. This question gains importance with the increasing numbers of older women in the population.

Methods: We addressed the question using data from three large U.S. cohort studies involving 310,290 white women aged 50+ years at recruitment, of whom 1,815 developed subsequent incident invasive epithelial ovarian cancer. We used Cox regression, stratified by cohort, to examine age-related trends in the HRs per full-term pregnancy and per year of oral contraceptive use.

Results: The parity-associated risk reductions waned with age (Ptrend < 0.001 in HR with increasing age), particularly among women aged 75 years or more, for whom we observed no association with parity. However, we observed no such attenuation in the oral contraceptive-associated risk reductions (P = 0.79 for trend in HR with increasing age).

Conclusion: These findings suggest that prior oral contraceptive use is important for ovarian cancer risk assessment among women of all ages, while the benefits of parity wane as women age.

Impact: This information, if duplicated in other studies, will be useful to preventive counseling and risk prediction, particularly for women at increased ovarian cancer risk due to a personal history of breast cancer or a family history of ovarian cancer. Cancer Epidemiol Biomarkers Prev; 25(7); 1059-63. ©2016 AACR.