According to the results of a study conducted in Canada, the sharp drop in use of combined (estrogen plus progestin) hormone therapy that occurred between 2002 and 2004 was accompanied by a decrease in breast cancer incidence. These results were published in the Journal of the National Cancer Institute.
As women reach menopause and beyond, more than 80% will experience symptoms such as hot flashes, night sweats, sleep disturbance, and vaginal dryness. Estrogen, with or without progestin, is an effective treatment for many of these symptoms. Over the last several years, however, studies have raised important concerns about the health effects of menopausal hormone therapy.
In 2002, a report from the Women’s Health Initiative indicated that combined hormone therapy increased the risk of breast cancer, heart disease, stroke, and blood clots. Use of combined hormone therapy decreased the risk of fractures and colorectal cancer, but these benefits were thought to be outweighed by the risks for most women.
After this report, use of combined hormone therapy declined markedly. Studies from several countries—including the United States—suggest that this decline in hormone use was followed by a decline in breast cancer incidence rates.
To evaluate trends in hormone use and breast cancer in Canada, researchers collected information about women between the ages of 50 and 69 who participated in the National Population Health Survey between 1996 and 2006.
The researchers conclude that between 2002 and 2004, a decline in hormone therapy use in Canada was accompanied by a decline in breast cancer incidence.
Additional research is warranted to determine the biologic link between hormone therapy and breast cancer. The results of the current study suggest that combined hormone therapy may speed the growth of breast cancers.
Reference: De P, Neutel I, Olivotto I, Morrison H. Breast cancer incidence and hormone replacement therapy in Canada. Journal of the National Cancer Institute [early online publication]. September 23, 2010.