Progestin-only birth control pills are a common form of hormonal contraception, but knowledge of their association with breast cancer risk has been limited. In a new study, researchers investigated the link between the use of hormonal contraception and the risk of breast cancer.
They found that using progestin-only contraception increased the risk of breast cancer as much as using combined contraception. It says that doctors should weigh the benefits and risks of using hormonal contraception for female patients. Experts say the findings are broadly consistent with known risks, which are small overall.
Between 2017 and 2019, about 65% of women aged 15–49 used some form of contraception, and 14% of them used the pill. Birth control pills come in two forms: a progestin-only pill and a combination pill containing both progestin and estrogen-based ingredients.
Progestin or gestagen is a synthetic version of progesterone, a naturally occurring hormone. A 1996 meta-analysis found that people using combined oral contraceptives had a slightly increased risk of breast cancer within 10 years of use.
In recent years, progestin-only birth control methods—including pills, injectables, implants, and intrauterine devices (IUDs)—have become more popular. In England, drug prescriptions increased from 1.9 million in 2010 to 3.3 million in 2020.
However, there has been limited research on the effect of progestin-only contraception on breast cancer risk. Recently, researchers investigated the link between the use of hormonal contraception and the risk of cancer.
Like the combined pill, they found that progestin-only birth control slightly increased the risk of breast cancer. The study was published in PLOS Medicine.
Breast cancer and hormonal contraception
For this study, researchers analyzed health records from a UK primary care database. They included data from 9,498 women under the age of 50 with breast cancer and 18,171 women without.
Altogether, 44% of women with breast cancer and 39% of women without a prescription used hormonal contraception. About half of these were for progestin-only products.
Finally, researchers found that taking combined birth control pills increased the risk of breast cancer by 23%. They also found that progestin-only oral contraceptive pills increased the risk of breast cancer by 29%. Other progestin-only products, including injectables, implants, and intrauterine devices (IUDs), increased the risk of breast cancer by 18%, 28%, and 21%, respectively.
The researchers added that five years of oral contraceptive use was associated with an incidence of breast cancer of 8 per 100,000 users aged 16 to 20 years and an incidence of 265 per 100,000 users aged 35-39 years.
