A large-scale epidemiological study published on Friday confirms this fact: the risk of breast cancer is increased in women who take hormonal treatment against the effects of menopause.
Compared to previous studies formulating this conclusion, the article published in the British journal The Lancet innovates by quantifying the risk for each type of treatment. It also shows that, if this adrift decreases after stopping treatment, it persists for at least ten years.
The authors reviewed 58 epidemiological studies on the subject, involving more than 100,000 women in total. Most of these studies are observational: they show a statistical link but do not demonstrate a causal link between the cancer of the women concerned and the treatment followed.
All THMs associated with increased risk
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 50-year-old woman who has continuous estrogen and progesterone THM for five years has a 8.3% chance of developing breast cancer within 20 years of starting treatment. The risk is only 6.3% for women of the same age who had no treatment.
According to the researchers, the proportion is 7.7% for those who have been given the same duration of treatment with estrogen and progesterone intermittently (not every day), and 6.8% for those treated with estrogen alone.
The risk increases with the duration of treatment
The risk also increases with the duration of treatment, says Gillian Reeves, of Oxford University, co-author of the study. "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," she says. But, it appears that the use of a THM for less than a year carries little risk.
At the time of menopause, the ovaries gradually stop functioning, leading to 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, an American study showed 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, THMs are becoming scarce
In France, one in four women aged 50 to 60 was treated in 2000 and 2001, and this type of treatment decreased by 62% between 2002 and 2006. At the same time, the incidence of breast cancer fell by 6.6% between 2003 and 2006 among women aged 50 to 69 years. The phenomenon is 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 must take into account the message of this study, but also (consider) the symptoms of menopause, carefully considering the risks and benefits of treatment for each woman," says Joanne Kotsopoulos, of Women's College Hospital. 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," adds this researcher specializing in breast cancer .