Research Activities, March 2014
Oral contraceptive use decreases risk of colorectal and endometrial cancer but slightly increases risk of breast cancers
Women who took an oral contraceptive (OC) may lower their risk of colorectal and endometrial cancers but may be slightly more likely to develop breast cancer than nonusers according to new analyses of combined data from a number of clinical studies.
Because OCs are the most common form of contraception that is both effective and reversible, they have been studied for their serious potential risks—such as venous thromboembolism, heart attack, stroke, and cancer, as well as their benefits.
In a systematic review of studies, Jennifer M. Gierisch, Ph.D., M.P.H., of the Duke University School of Medicine, and her colleagues synthesized 15 case–control studies and 8 cohort studies , finding an 8 percent increased risk of breast cancer in women with a history of any OC use compared with nonusers. In addition, breast cancer risk was higher with more recent use of OCs. Twelve studies assessed the risk of cervical cancer associated with OC use; however, only 3 studies focused on women positive for human papilloma virus (HPV), a cause of cervical cancer. The evidence was inconclusive about the risk of ever use of an OC on cervical cancer incidence in HPV-positive women.OC use reduced the risk of colorectal cancer by a significant 14 percent (based on 11 studies) and the risk of endometrial cancer by a significant 43 percent (based on 9 studies).
This study highlights some of the tradeoffs about nonreproductive outcomes that patients and providers need to consider with the use of oral contraceptives: increased risk for some cancers (breast and perhaps cervical) but decreased risk for others (colorectal and endometrial). Estimating the overall balance of benefit and harm is difficult. Timing of the outcomes affected by oral contraceptive use is variable—some risks and benefits are seen only during use (thromboembolic events), whereas others (cancers) occur in the future. The study was funded in part by AHRQ (Contract No. 290-07-10066).
More details are in "Oral contraceptive use and risk of breast, cervical, colorectal, and endometrial cancers: A systematic review," by Dr. Gierisch, Remy R. Coeytaux, M.D., Ph.D., Racheal Peragallo Urrutia, M.D., and others in the November 1, 2013, Cancer Epidemiology, Biomarkers, and Prevention 22(11), pp. 1931-1943.