Hormone replacement therapy can raise the risk of an uncommon type of breast cancer fourfold after just three years, U.S. researchers reported on Monday.
They found women who took combined estrogen/progestin hormone-replacement therapy for three years or more had four times the usual risk of lobular breast cancer.
For many years, doctors had thought hormone therapy could protect women from chronic diseases, especially heart disease.
But use of HRT plunged after the 2002 Women's Health Initiative study found that HRT could raise the risk not only of breast and ovarian cancer, but of strokes and other serious conditions.
Research since then shows the incidence of breast cancer dropped by 8.6 percent between 2001 and 2004 in the United States -- along with the decline in HRT use.
Doctors stress that younger women who need the drugs to relieve serious symptoms of menopause should still consider taking them because new, lower-dose formulations are available and doctors now know to prescribe them for short periods of time.