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Published on: October 14, 2015
Combined oral contraceptive use before the first birth and epithelial ovarian cancer risk
Linda S Cook1,2, Claire R Pestak3, Andy Cy Leung4
1Division of Epidemiology, Biostatistics and Preventive Medicine, Department of Internal Medicine and UNM Comprehensive Cancer Center, University of New Mexico, MSC 10 5550, 1 UNM, Albuquerque, NM 87131, USA.
Background:
Combined oral contraceptive (COC) use reduces epithelial ovarian cancer (EOC) risk. However, little is known about risk with COC use before the first full-term pregnancy (FFTP).
Methods:
This Canadian population-based case-control study (2001-2012) included 854 invasive cases/2139 controls aged ⩾40 years who were parous and had information on COC use. We estimated odds ratios (aORs) and 95% confidence intervals (CI) adjusted for study site, age, parity, breastfeeding, age at FFTP, familial breast/ovarian cancer, tubal ligation, and body mass.
Results:
Among parous women, per year of COC use exclusively before the FFTP was associated with a 9% risk reduction (95% CI=0.86-0.96). Results were similar for high-grade serous and endometrioid/clear cell EOC. In contrast, per year of use exclusively after the FFTP was not associated with risk (aOR=0.98, 95% CI=0.95-1.02).
Conclusions:
Combined oral contraceptive use before the FFTP may provide a risk reduction that remains for many years, informing possible prevention strategies.
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