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New Breast Cancer Risk Found With Hormone Replacement Therapy

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WebMD Health News

Jan. 25, 2000 (Washington) -- Using estrogen combined with progestin for hormone replacement therapy (HRT) for more than a few years increases a woman's risk of breast cancer far beyond what she would experience without the therapy, according to the largest study of the association between breast cancer and HRT. The lead investigator on the research, conducted by the National Cancer Institute, says the data call for a re-examination of long-term HRT use, but experts who reviewed the research for WebMD caution against overemphasizing the findings.

The concentrations of estrogen and progestin, the two main female sex hormones, fall as women go through menopause. (Progestin is a term that refers to any natural or synthetic hormone that acts like the natural hormone progesterone.) This decrease can lead to many adverse symptoms, some possibly life threatening and others that are less serious but troublesome and affect a woman's quality of life. The most common are hot flashes, vaginal dryness, bone loss leading to osteoporosis and fractures, and an increase in heart disease, partially due to a rise in cholesterol levels.

It is estimated that some 20% or more of women over the age of 45 take HRT, which can be in the form of estrogen alone or in combination with progestin. The benefit of HRT is derived mainly from the effects that estrogen has on the body. However, taking estrogen alone is associated with a fivefold increase in the risk of cancer of the uterus, and thus progestin must also be taken in women who have not had a hysterectomy.

HRT can be taken for several years or less to relieve the menopausal symptoms, but many women also stay on it for years for a variety of reasons, including the belief many physicians have that it protects women against heart disease and osteoporosis. Some preliminary research also suggests a lack of estrogen may play a role in Alzheimer's disease. Some women also report depression and anxiety and find relief with HRT.

The study, reported in the Jan. 26 Journal of the American Medical Association, involved over 46,000 women. Compared with women who received no hormone therapy, women who took estrogen and progestin in combination for an average of 3.5 years had a 40% greater chance of developing breast cancer, and those who used estrogen alone for an average of 10 years had a 20% higher risk of breast cancer.

The risks were also calculated by each increasing year of use. Women on estrogen alone had an increased risk of 1% a year for each year of use, compared with women on the estrogen-progestin combination, for whom the increase was 8% a year. The ill effects were seen most in women with long-term use, and the increased risk seemed to disappear within four years after HRT has been stopped.

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