Menopausal hormone therapy (MHT) was associated with an increased risk of breast cancer, according to data from more than 100,000 women with breast cancer taken from 58 epidemiological studies worldwide. Additionally, this increased risk may persist for more than 10 years after cessation of MHT, the study published in The Lancet showed.
“If the associations are largely causal, MHT use in western countries has already caused about 1 million breast cancers, out of a total of about 20 million since 1990,” wrote researchers from the Collaborative Group of Hormonal Factors in Breast Cancer.
To estimate these risks, the researchers analyzed data from all eligible prospective studies that looked at the type and timing of MHT use. Source studies were published between 1992 and 2018.
Of the postmenopausal women included in the studies, 108,647 were diagnosed with breast cancer. About…