Post menopausal women who take hormones for more than five years to relieve symptoms such as hot flashes have twice the risk of developing breast cancer as women who do not take estrogen and progestin to replace their own dwindling supplies, according to a new analysis of over 16,000 post-menopausal woman. The women were all in a 15-year study that was halted more than three years early in 2002 because of a clear link between the hormone replacement therapy (HRT) and the disease.

Researchers reported Saturday at the San Antonio Breast Cancer Symposium in Texas that taking HRT for just two years also hikes the odds of developing the disease. But the good news is that the risk dips when the women go off the drugs. The new data comes from a the Women's Health Initiative, a study launched by the National Institutes of Health in 1991 to gauge the effects of the hormone therapy and other factors on heart disease, bone fractures, and breast and colorectal cancer.  There had been earlier studies showing that HRT might prevent osteoporosis (bone-thinning ) and protect the heart. Researchers, however, abruptly stopped the study after finding that it did not guard against heart disease and that there was a 26 percent higher risk of breast cancer among the women taking hormones.

Scientists kept tabs on participants until 2005. Their findings: that women who had been taking the drugs for at least five years were twice as likely as those not on the meds to develop breast cancer; the risk dipped when the women stopped taking the pills, decreasing to normal levels two years after they went off them.

Despite the snowballing evidence linking hormone replacement therapy to breast cancer, many doctors continue to prescribe it for women with debilitating hot flashes and other symptoms of menopause. The Food and Drug Administration (FDA) suggests that women with severe hot flashes consider hormone therapy, but recommends they take only the smallest doses for the shortest amount of time.

Breast cancer is the second leading cause of cancer death after lung cancer among women in the U.S., according to the National Cancer Institute, which estimates that there will be 182,460 new breast cancer cases among U.S. women this year alone. Recent studies have linked breast cancer risk to a variety of other factors, including dense breast tissue and family history.

Image credit © Kostich