Birth Control and Cancer Risk
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.