Many women take birth control pills (oral contraceptives). Although evidence on the link between birth control pills and breast cancer risk continues to grow, the overall conclusion has remained the same for a number of years: current or recent use of birth control pills slightly increases the risk of breast cancer.
A large analysis that combined the results of many studies found that while women were taking birth control pills (and shortly thereafter), their relative risk of breast cancer was 10 to 30 percent (or 1.1-1.3-fold) higher than that of women who had never used birth control pills [124]. Once women stopped taking the pill, their risk began to decrease and returned to normal within about 10 years. In most of the studies, the women were taking older, higher-dose versions of the pill. One area under active study is how today's lower-dose pills might affect the risk of breast cancer. The evidence to date hasn't been able to answer this question.
While results from a large case-control study found no link between birth control pills and breast cancer [125], the findings from this single study are not compelling enough to change the general conclusions based on all the data to date. In fact, the findings in certain groups of women in this study actually support the conclusion of the combined analysis—that birth control pill use slightly elevates breast cancer risk.
While the increased breast cancer risk associated with pill use may be frightening, it is important to note that most women on the pill have a low risk of breast cancer to start with because they are typically young and premenopausal. So even with a slight increase in risk, they are still unlikely to develop breast cancer while they are on the pill.
There are several types of birth control pills that lower the number of periods a woman has during a year. At this time, there are too few data to comment on whether these pills affect breast cancer risk the same as other types of birth control pills.
Before making any decisions about birth control pills, women should weigh the pros and cons of using them. Though they have some risks associated with their use, birth control pills have a number of advantages as well, including preventing unwanted pregnancies and decreasing a woman's risk of both uterine and ovarian cancers [126,127].
Depo Provera and the Birth Control Patch
Similar to birth control pills, Depo Provera, an injected contraceptive, and the birth control patch contain hormones. Depo Provera contains progesterone alone, while the birth control patch contains both estrogen and progesterone.At this time, data on the potential link between these products and breast cancer risk are limited [128,129]. The pooled results of two studies on Depo Provera showed no significant impact on breast cancer risk overall.A possible increase in risk was found only among current users, but it is not clear whether this was due to increased screening and surveillance among the women using Depo Provera [130]. Women should speak to their health care provider to discuss the risks and advantages of these alternatives to birth control pills.
Updated 09/12/09
