Pooled analysis of 3 European case-control studies of epithelial ovarian cancer: III. Oral contraceptive use.

TLDR: The relationship between use of oral contraceptives and other contraceptive methods and the risk of ovarian cancer was examined in a combined analysis of 3 hospital‐based case‐control studies in Italy, the United Kingdom, and Greece, suggesting that the protection persists for 15 years or more after cessation of use and may be larger for use at younger age.

Abstract: The relationship between oral contraceptive (OC) use and other contraceptive methods and the risk of ovarian cancer was examined in a combined analysis of 3 hospital-based case-control studies conducted in Italy the UK and Greece. A total of 971 ovarian cancer cases and 2258 controls under age 65 were evaluated. Compared with never-users the combined multivariate relative risk (RR) for ever-users was 0.6 (95% confidence interval CI=0.4-0.8) and the estimates were consistent in the 3 datasets. The protection was also similar across strata of age and parity. Considering various measures of OC use available in the Italian and British datasets only the protection conveyed on ovarian cancer risk increased with the duration of use and persisted in the medium-long period; the RR in women reporting their last OC use > or=15 years prior to diagnosis was 0.5 (95% CI=0.2-1.0). The risks in ever-users were appreciably lower in those women who reported their 1st OC use before age 25 (RR=0.3 for 1st use before age 25 0.8 for 1st use at ages 25-34 and 0.7 at age 35 or after). Such findings emerged similarly from Italian and British data. This combined analysis besides offering further quantitative estimates of the protective effects of OCs on ovarian cancer risk among European populations provides useful insights into the time pattern of the relationship between OC use and ovarian carcinogenesis. This suggests that the protection persists for 15 or more years after cessation of use and may be larger for use at younger ages. (authors)