More than 80% of women will use hormonal birth control (like the pill) sometime during their reproductive years, but many women are unaware of the noncontraceptive benefits of using this type of contraception.
In general, combination hormonal contraceptives consist of a progestin and a synthetic estrogen. Some research shows that hormonal contraceptives also may have the added benefit of reducing the risk of colorectal cancer (although the data is limited and more research is needed).
Please be aware that the main reason to use hormonal birth control is for contraception (to prevent an unintended pregnancy) -- possible noncontraceptive benefits can be considered when determining which hormonal method to choose.
The following is a list of specific prescription birth control methods that some research has been shown to be effective in lowering the risk of colorectal cancer:
- Combination Birth Control Pills: A meta-analysis of 20 studies investigating the relationship between the risk of colorectal cancer and combination birth control pill use revealed that there is an 18% reduction in the risk of developing colorectal cancer among those who use oral contraceptives. This protective effect was greatest for recent pill use and showed no duration effect (meaning, it does not matter how long you had been using the pill).
Other studies also suggest that those who are currently or recently using combination birth control pills are more likely to have a lower risk of colorectal cancer. Past use of combined OCs does not appear to result in a reduction of colorectal cancer risk.
The reduced risk of colorectal cancer in Pill users is thought to be due to a few reasons. Bile acids are made by the liver and work with bile to break down fats. Continuous exposure to bile acids can be carcinogenic on the tissues in the colon, thereby causing colorectal cancer. The estrogen and progestin in the pill, however, may reduce the secretion of bile acids.
Another cause of colorectal cancer may be due to mutated or damaged repair genes. Microsatellite instability is a condition where a cell has difficulty repairing DNA because it is damaged. About 90% of tumors from people who have certain types of colorectal cancer show microsatellite instability. Research suggests that the combination of estrogen and progestin has been related to a decrease in microsatellite instability.
- Low-Dose vs. Higher Dose Pills: Lower dose birth control pills contain the lowest amount of estrogen (20 mcg) plus one of the 8 types of progestin. Regular dose pills contain a progestin and 30–35 mcg estrogen, and high dose pills have around 50 mcg of estrogen plus progestin. There does not appear to be a lot of information on the type of pill formulation and the lowered risk of colorectal cancer. Research seems to indicate that there is not a different level of colorectal cancer risk reduction from different estrogen or progestin doses in the pill. The protective effect against colorectal cancer risk has been seen in studies ranging from the 1960s (when mostly high dose pills were in use) to 2008 (when newer pill formulations with lower hormone levels were more typically used).
- NuvaRing and Ortho Evra Patch: Given that both of these birth control methods contain a combination of progestin and estrogen, it is thought that they should allow the same protective benefit from colorectal cancer as combination birth control pills do. Research, however, is limited.
Bosetti C, Bravi F, Negri E, La Vecchia C."Oral contraceptives and colorectal cancer risk: a systematic review and meta-analysis." Hum. Reprod. Update (2009) 15(5):489-498. Accessed 2/25/11.
Fernandez E, La Vecchia C, Balducci A, Chatenoud L, Franceschi S, Negri E. "Oral contraceptives and colorectal cancer risk: a meta-analysis." Br J Cancer 2001;84:722–7. Accessed via private subscription.
Hannaford P, Elliott A. "Use of exogenous hormones by women and colorectal cancer: Evidence from the Royal College of General Practitioners’ Oral Contraception Study." Contraception 2005;71:95–8. Accessed via private subscription.
McMichael AJ, Potter JD. "Host factors in carcinogenesis: Certain bile-acid metabolic profiles that selectively increase the risk of proximal colon cancer." J Natl Cancer Inst 1985;75:185-191. Accessed via private subscription.
Newcomb PA, Zheng Y, Chia VM, Morimoto LM, Doria-Rose VP, Templeton A, Thibodeau SN, Potter JD. "Estrogen plus progestin use, microsatellite instability, and the risk of colorectal cancer in women." Cancer Res 2007;67:7534-7539. Accessed via private subscription.
The American College of Obstetricians and Gynecologists. "Noncontraceptive uses of hormonal contraceptives." Practice Bulletin No. 110, Jan 2010 115:206-18. Accessed via private subscription.