Birth Control and Cancer Risk

By Hoag

Categories: Breast Program

Birth control pills give you breast cancer!! Birth control pills protect you from ovarian cancer!! There was a lot in the news in the past year about birth control pills and how they impact cancer risk. A major study published in December 2017 stated women currently or recently using the pill had an increased risk of breast cancer. (1) A sister study published in September 2018 (same researchers, same patients) showed that using newer formulations of the pill lowered risks of ovarian cancer (we already knew older pills did). (2) They were both major news stories. However, they left many women confused regarding the safety of using the birth control pill, especially women already at increased risk for breast and ovarian cancers.

One way to weigh the risks and benefits is to look at the magnitude of those upsides and downsides. Yes, the pill increases some risks and decreases others, but by how much? The data around breast cancer risk is mixed with some studies showing no real increase in risk and others showing a very small rise. This particular study showed 13 additional cases of breast cancer in a group of 100,000 women beyond what they expected to see due to age. In other words, for a 40-year-old woman, taking the pill increased her breast cancer risk by less than 1%. This study was criticized because they were unable to discount other factors in their patients that are known to increase breast cancer like alcohol intake, physical activity and breast-feeding.

The data describing the protective effects of the pill against ovarian cancer are much more consistent. Studies have shown a decrease in ovarian cancer risk among users of the pill by as much as 40-50% after 5 years of use. This latest study shows that the newer pill formulations with lower levels of estrogen and different versions of progestin also lower ovarian cancer risk. Importantly, that protection persists for years after the pill is stopped. Since ovarian cancer is a disease for which no effective screening test exists, many women are diagnosed at advanced stage, so preventing ovarian cancer may be lifesaving.

This discussion should be put in the context of the overall benefits and risks of oral contraception. Birth control pills reduce endometrial and colon cancers as well as ovarian cancer, and are a mainstay of treating abnormal bleeding that can lead to anemia and other significant health problems. Birth control pills when used consistently are very effective in preventing unwanted pregnancy, which carries its own risks. The Center for Disease Control reports that in 2014, 144 per 10,000 women suffered a pregnancy complication with severe short or long-term consequences for their health. (3)

That is almost 10 times the estimate of how many women may get breast cancer from the birth control pill. Established risks of the oral contraceptive pill are related to blood clotting events, estimated to range from 2- 17 women per year per 10,000 who take the pill (less than 0.1%). (4)

To summarize, birth control pills, like most things in life, are a mixed bag: a likely small increase in breast cancer risk while taking the pill along with a significant decrease in ovarian cancer risk (as well as endometrial and colon cancers) that persists even after the pill is stopped, and effective prevention of pregnancy. What these benefits and risks mean to each individual woman is entirely up to her. For our patients at risk for ovarian cancer, it is likely that the benefits significantly outweigh the risks.

Birth Control Pills Still Linked to Breast Cancer, Study Finds

Birth Control Pills Reduce Risk of Ovarian Cancer in Fifth of Women Studied

Contemporary Hormonal Contraception and the Risk of Breast Cancer (New England Journal of Medicine)

Association between contemporary hormonal contraception and ovarian cancer in women of reproductive age in Denmark: prospective, nationwide study (British Medical Journal)

  1. Morch LS, et al. Contemporary Hormonal Contraception and the Risk of Breast Cancer. The New England Journal of Medicine 2017; 377(23):2228-2239
  2. Iverson L, et al. Association between contemporary hormonal contraception and ovarian cancer in women of reproductive age in Denmark: prospective nationwide cohort study. British Medical Journal 2018; 362:3609.
  3. Center for Disease Control. Severe Maternal Morbidity in the United States. 2014. Available at: https://www.cdc.gov/reproductivehealth/maternalinfanthealth/severematernalmorbidity.html
  4. Vinogradova, Y et al. The use of combined oral contraceptives and risk of venous thromboembolism: nested case control studies using the QResearch and CPRD databases. British Medical Journal 2015; (350):2135