A large study demonstrates the relationship between menopausal hormone therapy and breast cancer

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An international collaboration, using data from more than 100,000 women with breast cancer from 58 epidemiological studies worldwide, has found that the use of menopausal hormone therapy (MHT) is associated with an increased risk of breast cancer, and that a Some increased risk persists for more than a decade after its use is discontinued.

The findings, published in the magazine The Lancet, suggest that all types of MHT, except topical vaginal estrogens, are associated with higher risks of breast cancer, and that the risks are higher for users of estrogen-progestin hormone therapy than for hormone therapy with estrogen alone. For estrogen-progestin therapy, the risks were greater if the progestogen was included daily instead of intermittently (for example, 10 to 14 days per month).

In Western countries, the use of MHT increased rapidly during the 1990s, abruptly reduced by half in the early 2000s and stabilized during 2010. Although some women use them in the short term, nowadays about five years of use are common, while before they were common for about ten.

In this new study, the authors gathered and centrally re-analyzed all prospective studies from 1992 to 2018 that had registered the use of menopausal hormone therapy, and then monitored the incidence of breast cancer, with 108,647 women who subsequently They developed breast cancer at an average age of 65 years. They observed the type of MHT used for the last time, the duration of use and the time elapsed since the last time it was used in these women.

Among women who developed breast cancer in prospective studies, half had used MHT, the average age at menopause was 50 years and the average age at the start of MHT was also 50 years. The average duration of the use of hormonal therapy was 10 years in current users and seven years in those who have ever used it but stopped.

For women of average weight in Western countries who have never used MHT, the average risk of developing breast cancer during the 20 years between 50 and 69 is approximately 6.3 per 100 women: that is, Around 63 per 1,000 women who never use hormone therapy develop breast cancer.

However, this new research estimates that for women with five years of use of the three main types of MHT, from 50 years of age, the risk of breast cancer from 50 to 69 years would even increase from 6 , 3 percent up to: 8.3 in estrogen users plus daily progestogen; 7.7 in estrogen plus intermittent progestogen; and 6.8 in estrogen only. In addition, the increase in breast cancer risk would be approximately double for women who use MHT for 10 years instead of 5.

Since menopause usually occurs between the ages of 40 and 50, almost all the evidence was for women who had had menopause and had initiated MHT in this age range. The proportional increase in risk was similar for women who started hormone therapy at the ages of 40-44, 45-49, 50-54 and 55-59 years. However, the risk seemed to be somewhat attenuated among the few who had started using MHT after age 60. The risk also decreased due to the body mass index, particularly in the case of estrogen-only hormone therapy, which had little effect on obese women.


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