避孕药降低卵巢癌风险

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The Pill and Ovarian Cancer: Persistent Protection
Reanalysis of 45 studies verified that oral contraceptives provide protection when women need it most: decades after use.

Although oral contraceptives (OCs) have been shown to reduce the risk for epithelial ovarian cancer, the duration of this protective effect has not been clearly defined. Now, investigators have reanalyzed data from 45 case-control and prospective studies (primarily in Europe and the U.S.) including more than 23,000 women with ovarian cancer (cases; mean age at diagnosis, 56) and 87,000 women without the disease (controls). Overall, 31% of the cases and 37% of the controls had used the pill; average duration of OC use was 4.4 and 5.0 years, respectively.

Overall, the relative risk for ovarian cancer in OC ever-users versus never-users was 0.73 (95% confidence interval, 0.70–0.76; P<0.0001). Table 1 shows the estimated absolute risk for ovarian cancer before age 75 in never-users and ever-users.

Longer duration of OC use was associated with lower risk for ovarian cancer: For example, relative risk was approximately halved in women who had used OCs for 15 years. Although protection attenuated with time, reduced risk still existed more than 30 years after OC use was stopped. Adjustment for several potentially confounding factors (e.g., ethnic group, use of hormone therapy, BMI) had little effect on these observations. In analyses based on calendar year of OC use as a proxy for estrogen dose, the findings were similar regardless of OC formulation.

Comment: The results of this massive reanalysis show that women who use OCs have a reduced risk for ovarian cancer decades later, when the incidence of this uncommon but lethal disease peaks. The authors estimate that since the pill first became available almost 50 years ago, some 200,000 incident cases and 100,000 deaths from ovarian cancer have been prevented worldwide. The authors go on to speculate that in the future, use of the pill will prevent more than 30,000 ovarian cancers annually. Because OCs can prevent ovarian malignancy in both high- and low-risk women, these findings are especially relevant to women at elevated risk for ovarian cancer — including low-parity women and those who have a positive family history or who carry a deleterious BRCA mutation.

— Andrew M. Kaunitz, MD

Published in Journal Watch Women&#39;s Health January 31, 2008