Oral contraceptives (OCs) have been associated with roughly a 27% reduction in risk for developing ovarian cancer in the female population, overall.1 Studies over the years have revealed a number of other cancers in women for which OC use provides a protective benefit, principally endometrial and colorectal cancers.1-3
American researchers, led by Jennifer M, Gierisch, PhD, MPH, of Duke University Medical Center, Durham, NC, conducted a systematic review of data published since 2000 regarding OC use and risk for endometrial, colorectal, breast, and cervical cancers. Their findings were published online last month in Cancer Epidemiology, Biomarkers and Prevention.4 They found that data collected since 2000 are consistent with OC use which conveyed a benefit in the reducing endometrial and colorectal cancer risks, although increasing the risk of breast cancer by a small, yet significant, amount.
For endometrial cancer, their analysis included data for 3.98 million person-years and found a relative risk (RR) associated with ever- versus never-use of OCs equal to 0.57 (95% CI, 0.43-0.77; P<0.001).4 According to a report from an Agency for Healthcare Research and Quality report, with which this review is associated, duration of use appears to correlate with the degree of protection, but the strength of evidence supporting this association was considered low.1
A 14% reduction in risk of colorectal cancer (RR=0.86; 95% CI, 0.79-0.95; P<0.046) was calculated from 2.97 million person-years of data.4 These data showed no association between duration of use and risk reduction,4 consistent with earlier analyses.2,3
However, not all the news was good news. Ever-use of OCs compared to never-use of OCs was associated with an increase in breast cancer (RR=1.08; 95% CI, 1.00-1.17; P<0.001) in 3.98 million person-years of data. Duration of OC use positively correlated with an increase in breast cancer risk, although risk diminished once OCs were discontinued and was neutral 20 years after discontinuation.4 Researchers calculated that use of OCs would increase lifetime absolute risk for breast cancer by 0.89%.4 In addition, OC use for 5 years or longer was associated with an increase in cervical cancer among women infected with the human papilloma virus.4
In summary, data from the past 12 years are consistent with earlier data suggesting that the noncontraceptive effect of OC use on cancer risk is mixed. Women’s individual cancer risk factors should be considered when OCs are indicated for contraception or other uses.
- Havrilesky LJ, Gierisch JM, Moorman PG, et al. Oral Contraceptive Use for the Primary Prevention of Ovarian Cancer. Executive Summary. Evidence Report/Technology Assessment No. 212. AHRQ Publication No. 13-E002-EF. Rockville, MD: Agency for Healthcare Research and Quality; June 2013. http://effectivehealthcare.ahrq.gov/ehc/products/416/1530/cancer-ovarian-contraceptives-executive-130611.pdf. Accessed October 24, 2013.
- Cibula D, Gompel A, Mueck AO, et al. Hormonal contraception and risk of cancer. Human Reprod Update. 2010;16(6):631-650.
- Bosetti C, Bravi F, Negri E, La Vecchia C. Oral contraceptives and colorectal cancer risk: a systematic review and meta-analysis. Human Reprod Update. 2009;15(5):489-498.
- Gierisch JM, Coeytaux RR, Urrutia RP, et al. Oral contraceptive us and risk of breast, cervical, colorectal, and endometrial cancers: a systematic review. Cancer Epidemiol Biomarkers Prev. 2013;Oct 8: doi: 10.1158/1055-9965.EPI-13-0298 [Epub ahead of print]