Women undergoing hormonal treatment against the effects of menopause have a slightly higher risk of developing breast cancer, confirms a large-scale epidemiological study published Friday.
The authors reviewed 58 epidemiological studies on the subject, involving more than 100,000 women in total.
Most of these studies are observational, that is to say, they highlight a statistical link but do not show a causal link between the cancer of the women concerned and the treatment followed.
According to their findings, all menopausal hormone therapies (THMs) are associated with increased risk, with the exception of estrogen gels for topical application.
For example, a woman in her 50s who has been on continuous estrogen and progesterone THM for five years has a 8.3% chance of developing breast cancer within 20 years of starting treatment, while risk is only 6.3% for women of the same age who had no treatment.
The proportion would be 7.7% for those who have been treated for the same duration with estrogen and progesterone intermittently (not every day), and 6.8% for those treated with estrogen alone, say the researchers.
The risk also increases with the duration of treatment: "the use of a THM for 10 years leads to an excess risk of breast cancer about twice as high as that associated with a five-year treatment. that using THM for less than a year is a low risk, "says Gillian Reeves of Oxford University, co-author of the study.
At the time of menopause, the ovaries gradually stop functioning, causing a drop in estrogen levels and a virtual disappearance of progesterone. These hormonal upheavals can cause very uncomfortable symptoms (hot flushes, sleep disturbances, vaginal dryness, etc.), which hormone replacement treatments can relieve.
But in 2002, a US study threw the blame on the fact that THM increased the risk of breast cancer.
In the years that followed, their prescription fell sharply. They are now reserved for troublesome disorders and prescribed at the smallest doses and for the shortest possible duration, with a reassessment each year.
In France, while at least a quarter of women aged 50 to 60 were treated in 2000 and 2001, this type of treatment decreased by 62% between 2002 and 2006.
At the same time, the incidence of breast cancer fell sharply, by 6.6%, between 2003 and 2006 among women aged 50 to 69, a phenomenon at least partly attributed to the scarcity of THMs.
Other factors such as alcohol consumption, weight or age of the first child are also likely to affect the occurrence of breast cancer.
"Physicians should consider the message of this study, but also (consider) the symptoms of menopause, carefully considering the risks and benefits of treatment for each woman," said Joanne Kotsopoulos of Women's College Hospital. from Toronto (Canada), in a comment on the article.
"It can depend on the severity of the symptoms, contraindications to THM, BMI (body mass index, NDLR) and may take into account the preferences of the patient," said the researcher specializing in cancer breast.