In follow-up studies of the women involved in the large federally funded Women’s Health Initiative, researchers found that hormone replacement therapy (HRT) used after menopause not only increased the risk of breast cancer in treated women, but also increased their risk of dying from the disease, compared with women who did not take HRT.
The study found that women who took Prempro — a commonly prescribed hormone replacement pill containing a combination of estrogen and progestin — were more likely to develop invasive breast cancer: 0.42% of women on HRT were diagnosed with cancer, compared with 0.34% of the placebo group. Among the women who developed breast cancer, those on HRT were more likely to have cancer that had spread to the lymph nodes (23.7%) than the placebo group (16.2%), indicating a later-stage disease. Also, women who developed breast cancer and took HRT were more likely to die from their cancer or from any cause after diagnosis than women those who did not take the medication. (More on Time.com: Photos: The Landscape of Cancer Treatment)
It is not clear exactly how the drugs affected cancer severity or death risk, but previous studies have suggested that hormone therapy can make breast tissue denser, which in turn may make tumors harder to find on a mammogram, delaying diagnosis. The hormone estrogen may also promote the growth of certain breast tumors or help them spread more quickly.
The WHI, which included more than 16,500 postmenopausal women who took either hormone replacement therapy or a placebo, was halted in 2002, three years early, after researchers found that the hormones were increasing risks of breast cancer, stroke, heart disease and pulmonary embolism. Follow-up studies of the women have provided increasing clarity on the risks and benefits of HRT, including the newest study published Tuesday in the Journal of the American Medical Association. (More on Time.com: Breast-Feeding after Breast Cancer Is O.K.)
After the WHI was initially halted, the number of women taking HRT dropped precipitously. Millions of women still opt for treatment, however, to combat symptoms of menopause in the short term. Now the question remains: how long can women take HRT before putting themselves at increased risk of breast cancer or death. The New York Times reported:
Another author of the new study, Dr. JoAnn E. Manson, a professor of medicine at Harvard Medical School and Brigham and Women’s Hospital, said women should not take the hormones at all unless they really need them, for moderate to severe symptoms like hot flashes and night sweats that disrupt sleep and severely affect their quality of life.
At the same time, she said, the new information should not necessarily alarm women who have taken the hormones, because the new report found only one to two additional breast cancer deaths per 10,000 women per year among those taking hormones.
“The data suggest it is cumulative long-term use,” Dr. Manson said. “Women should avoid long-term use. I think that’s the bottom line.”
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