All hormonal contraceptives carry a slightly increased risk of breast cancer, including the increasingly popular progestogen-only pills
No one wants to be told that something they are taking will increase their risk of breast cancer. But the problem exists. “On average, 44% of women with breast cancer and 39% of matched controls had a hormonal contraceptive prescriptionwith about half of prescriptions for progestogen-only preparations,” says the study published Tuesday in the journal PLOS Medicine that fills a research gap investigating the link between breast cancer and progestogen-only contraceptives.
Translated: all forms of birth control with hormonal contraception carry an increased risk of breast cancer in women, even if it is mild, including the increasingly used methods based on progestogen only (a natural or synthetic substance that produces effects on the body similar to those of progesterone). The progestin pill or mini-pill is a latest generation method of contraception.
The study analyzed data from nearly 10,000 UK women, people under 50 or diagnosed with invasive breast cancer between 1996 and 2017, plus over 18,000 cases of women who have not had breast cancer. “A puzzling finding in the current analysis,” the study points out, “however, is the excess risk of breast cancer associated with the use of progestogen-releasing contraceptive IUDs, which is similar in magnitude to the excess risks found for oral and for other parenteral progestogens”.
However, this slight increase in breast cancer risk must be put into perspective against the benefits from contraception, including the protection it provides against other types of cancer, the researchers point out. Oral contraceptives actually provide quite substantial, long-term protection from other female cancers, such as ovarian cancer and endometrial cancer.
The increased risk of breast cancer was already well known for contraceptive methods combining progestin and estrogen. But while the use of progestogen-only methods has been on the rise for years, little work so far has focused on their specific effect on breast cancer risk.
According to this new work, women who use hormonal contraception have an increased risk of developing breast cancer by about 20-30%. regardless of the mode of administration (pill, IUD, implant, or injection) or formula used (estrogen or progestogen only). This rate is similar to that of previously published work, including a large 1996 study.
“Even if this (study) confirms an increase, we don’t want women to suddenly stop taking contraceptives because of itand there is no indication in these findings that women need to change their contraceptive or do something different,” said one of the study’s authors, Gilliam Reeves, in an interview with a trade journal. “These new types of contraceptives appear to behave very similarly to each other in terms of their effect on breast cancer risk.”
To give a more detailed idea of what that entails, the researchers calculated the number of additional breast cancer cases involved, knowing that the risks of developing the disease really increase as we age. In the case of hormonal contraception taken for five years between the ages of 16 and 20, the number of women who will develop breast cancer out of 100,000 will be 8. A very low number. Taken between the ages of 35 and 39, we have 265 additional cases of breast cancer for every 100,000 women.
Furthermore, the study confirms, as others have done before, that the increase in breast cancer risk linked to hormonal contraception is transient, ie it decreases in the following years when contraception is stopped. “Increased risk,” explains the analysis, “in current or recent users decreases after cessation of use 10 or more years after cessation.”
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