Does Taking the Pill Decrease Cancer Risk? It Depends

A large scale study recently found evidence that cancer risk among users of oral contraceptives is significantly lower than women who have never taken the pill. The finding confirms what doctors and researchers have thought for years: that there to be a link between lowered cancer risk and oral contraceptive usage. However, long-term usage of the birth control pill, anything over 8 years, resulted in a statistically significant increased risk of developing any cancer.

The timing of the study's release adds to the public dialogue for Ovarian Cancer Awareness Month in September and Breast Cancer Awareness Month in October. The findings were published Sept. 10 and full results of Oral Contraceptives Study are available online this month at the British Medical Journal.

Oral Contraceptives Study

Women who used oral contraceptives at some time in their lives had statistically significant lower rates of cancers, including bowel/rectal, uterine and ovarian cancer, in comparison with women who have never used it. The Oral Contraceptive Study, conducted by the Royal College of General Practitioners, included two data sets: one with a general practitioner dataset and detailed information, and the other through the National Health System registry of death and cancer incidence. The study spanned 36 years and followed more than 46,000 women.

The findings re-iterate previously known contradicting risks and benefits of birth control pill usage for the different types of cancer. For instance, most research indicates women taking oral contraceptives for extended periods of time have a reduced risk of developing ovarian cancer, but a slightly elevated risk for breast cancer and cervical cancer. However, the risks of breast cancer and cervical cancer decline after stopping oral contraception, returning to that of women who do not take the pill within approximately 10 years.

When the general practitioner observation dataset was used, women who had taken the pill at some time during their lives had a 3 percent reduced risk of developing any cancer. When the larger main dataset was used, the reduction was 12 percent. A 12 percent reduction equates to approximately one fewer case of cancer for every 2,200 women who have used the pill for a year and 3 percent equates to one fewer case of cancer for every 10,000 women. All of this is good news, particularly as evidence suggests that the protective effect of taking the pill lasts for up to 15 years after stopping.

Benefits

The reason that oral contraceptives are believed to reduce risk of certain cancers is that the pill limits hormonal fluctuations. According to information from the National Cancer Institute, "estrogen stimulates the growth and development of the uterus at puberty, causes the endometrium (the inner lining of the uterus) to thicken during the first half of the menstrual cycle, and influences breast tissue throughout life, but particularly from puberty to menopause." Research indicates that some cancers depend on sex hormones for their development and growth. Taking the pill has been shown to significantly reduce the risk of ovarian and endometrial cancer. The protective effect increases with the length of time women take oral contraceptives, and continues for many years after a woman stops their usage.

Risks

Hormonal factors that increase the risk of breast cancer and cervical cancer include conditions that may allow high levels of hormones to persist for long periods of time. Taking oral contraceptives is keeps hormones is one such condition, and multiple studies have indicated women using birth control pills for five or more years have an elevated risk of developing breast cancer. The National Cancer Institute breaks down risk percentages by cancer type and provides additional information about research.

A woman's individual balance of cancer risks and benefits varies depending on patterns of oral contraception usage, as well as personal behaviors and family history of different cancers.

Sources:

British Medical Journal

Newswise

National Cancer Institute