Oral Contraceptives Reduce Ovarian Cancer Risk

The risk of developing ovarian cancer was reduced by more than a fourth for women who had ever taken oral contraceptives and by more than half for those who had taken them for at least 10 years.

The findings of a new review article suggest that women taking birth control pills have a reduced risk for developing ovarian cancer. The review, published online on June 3, 2013, in Obstetrics and Gynecology, included data collected from 55 previous studies conducted on oral contraceptive use in women.

Researchers from Duke University searched PubMed, Embase, the Cochrane Database of Systematic Reviews, and ClinicalTrials.gov for controlled studies or meta-analyses that reported a link between oral contraception use and incidence of ovarian cancer. Studies included were limited to those published from January 1990 to June 2012 to ensure the pills studied had similar formulations to those commonly used today. A pair of researchers was assigned to review each relevant article to decide whether the study would be included in the analysis.

Meta-analyses were conducted to test the relationship between ovarian cancer incidence and use of oral contraceptives, duration of contraceptive use, formulation used, age at first use, and time passed since last use. Primary analyses were limited to studies conducted from 2000 to 2012, but sensitivity analyses included data from older studies.

After analyzing 24 controlled studies, the researchers found that women who had ever used oral contraceptives had a risk of ovarian cancer that was reduced by almost 28% compared with those who had never taken birth control pills. In addition, the risk of developing ovarian cancer was reduced by more than half for women who had been taking an oral contraceptive for 10 years or longer.

The researchers also observed that women who began taking oral contraceptives at younger ages had a decreased risk of ovarian cancer. However, the effects of age at first use could not be differentiated from the effects of duration of use. Analysis of 2 large population cohort studies also showed a significant decrease in mortality caused by ovarian cancer in women taking oral contraceptives. Overall, the researchers determined that approximately 1 case of ovarian cancer is prevented for every 185 women who take oral contraceptives for 5 years.

Although a significant association between oral contraceptives and reduced risk of ovarian cancer was confirmed in the review, the authors caution against using the results as a basis for clinical decisions. More research, specifically on the effects of duration, needs to be conducted before researchers can recommend taking an oral contraceptive as a means of preventing ovarian cancer. Until then, the findings can serve as additional information for women to consider when weighing the benefits and risks of birth control pills.