All forms of hormonal contraception carry a slightly increased risk of breast cancer in women, including the increasingly used progestogen-only methods, according to a new study published Tuesday.
However, this slightly increased risk of breast cancer must be put into perspective against the benefits derived from contraception, including the protection provided against other types of cancer, the researchers note.
An increased risk of 20 to 30%
The increased risk of breast cancer was already well known for combined progestin and estrogen birth control methods. But while the use of progestin-only methods has been on the rise for years, little focus has so far been placed on their specific effect on breast cancer risk.
In reality, this turns out to be similar to the estrogen and progestogen methods, concludes this study published in the journal medicine plos. According to this work, women who use hormonal contraceptives have an increased risk of about 20% to 30% of developing breast cancer, regardless of the mode of delivery (pill, IUD, implant, or injection), or the formula used ( estrogen-progestin or progestin-only).
This rate is similar to what previous work, including a large study, had estimated as early as 1996.
Risks increase with age
To give a better idea of what this represents, the researchers calculated the number of additional cases of breast cancer involved, knowing that the risks of developing this disease increase with age.
In the case of hormonal contraception taken for five years between the ages of 16 and 20, the number of women out of 100,000 who will develop breast cancer will be eight. Taken between the ages of 35 and 39, this represents an additional 265 cases of breast cancer per 100,000 women.
“No one wants to hear that something they are taking will increase their risk of breast cancer,” said Gillian Reeves, a professor at the University of Oxford and co-author of the study. But it is a “very small risk in terms of absolute risk,” she stressed during a press conference.
This risk must also be considered in light of the benefits of hormonal contraception, “not only in terms of pregnancy control, but also because oral contraceptives provide quite significant long-term protection against other cancers in women, such as that of endometrium”. ovarian cancer,” said Gillian Reeves.
A risk that decreases when contraception is stopped
Furthermore, the study confirms, as others have done before, that the increased risk of breast cancer associated with hormonal contraception is transient: it decreases in subsequent years when contraception is discontinued. These results “are reassuring because the effect is modest,” said Stephen Duffy, a professor at Queen Mary University of London, who was not involved in this work.
This study was carried out using data from just under 10,000 women under the age of 50 who developed breast cancer between 1996 and 2017 in the UK, where progestin-only contraceptives are now as widely used as progestin-oestrogen combinations.
Progestin-only contraceptives are recommended for women who are breastfeeding, or for those with contraindications to estrogen-progestin pills, such as cardiovascular disease risks, or in case of smoking after the age of 35.
Among the “multiple factors” explaining the increase in use, it may be that “women now take contraceptives later” in their lives, and therefore have more of these conditions naturally, Gillian Reeves argued.
Source: BFM TV
