(WOMENSENEWS)–Hormone replacement therapy–which an estimated 6 million women use to treat symptoms of menopause–has been found to increase the risk of breast cancer, according to a study by the Women’s Health Initiative, part of the National Heart, Lung, and Blood Institute.
The government study, which started in 1997 and was supposed to continue until 2005, was immediately halted when results showed a small but significant increase in invasive breast cancer, as well as an increased risk of blood clots and strokes.
The study found that for every 10,000 women who take hormone replacement therapy in a year, eight more will be diagnosed with invasive breast cancer than those taking a placebo. Seven more will have a heart attack, eight more will have a stroke, and 18 more will have blood clots, compared to the control group. The risks for these diseases increased after women had been taking the drug for five years.
The study also found a slight decrease in risk for colorectal cancers and hip fractures among women taking hormone replacement therapy.
For several years doctors have prescribed hormone replacement therapy to women entering menopause, believing that it would protect women from heart disease and osteoporosis and help them feel younger and healthier in general. Some doctors interviewed by the New York Times said they would continue to prescribe the drug therapy, which consists of estrogen and progestin, because the risks are slight.
Others said they would now urge women not to take the drug therapy for more than four years, or would stop recommending it altogether.