Hormonal contraceptives increase the risk of breast cancer – 03/21/2023 – Equilibrium and Health

All hormonal contraceptives result in a slightly higher risk for breast cancer, including those containing only progesterone, which are increasingly used, according to a study published on Tuesday (21).

The authors of the paper emphasized that the increased risk of breast cancer must be weighed against the benefits of hormonal contraceptives, including the protection they offer against other types of female cancer.

The increased risk of breast cancer was well known for contraceptives that combine progesterone and estrogen, but although the use of progesterone-only contraceptives has been increasing for more than a decade, until now little research has focused on their specific effect. in the risk of breast cancer.

The new study, published in the journal PLOS Medicine, found that a woman’s risk of developing breast cancer is about the same between contraceptives that contain both estrogen and progesterone and those that contain only progesterone.

According to research, women who use hormonal contraceptives have an increased risk of about 20% to 30% of developing breast cancer, regardless of the method chosen (pill, IUD, implant or injection) or the formula used (estrogen-progesterone or only progesterone).

The findings are similar to those already published, including in a large study from 1996. Taking into account that the probability of developing breast cancer increases with age, the study authors calculated the absolute excess risk associated with hormonal contraceptives.

For women who took hormonal contraceptives over a five-year period between ages 16 and 20, this represented 8 cases of breast cancer in every 100,000. Between 35 and 39 years old, there were 265 cases per 100,000.

temporary risk

“No one wants to hear that something they take will increase their risk of breast cancer,” said Gillian Reeves, a professor at the University of Oxford and co-author of the study. But “what we’re talking about here is a very small increase in absolute risk,” she emphasized at a press conference.

“These increases in breast cancer risk, of course, have to be seen in the context of what we know about the many benefits of using hormonal contraceptives, not just in terms of birth control, but also because we know that oral contraceptives, in In fact, they offer substantial and long-term protection against other female cancers, such as ovarian and endometrial cancer,” added the professor.

The study also confirmed, as did others, that the risk of breast cancer decreases in the years after stopping the use of hormonal contraceptives.

Stephen Duffy, a professor at Queen Mary University of London who was not involved in the study, described the findings as “reassuring because the effect is modest”.

The study involved data from nearly 10,000 women under 50 who had breast cancer between 1996 and 2017 in the UK, where use of progesterone-only contraceptives is as widespread as the combined method.

Progesterone-only contraceptives are recommended for women who are breastfeeding, who are at risk for cardiovascular problems, or for smokers over age 35.

Among the factors that explain the increase in its use may be the fact that “women are taking contraceptives later”, which naturally means that they present these conditions in greater quantity, indicated Gillian Reeves.