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Increased risk of breast cancer from hormone therapy continues over time [Updated]

October 19, 2010
  • Image of a breast cancer cell.
Image of a breast cancer cell. (National Cancer Institute )

Estrogen-plus-progestin hormone replacement therapy increases the risk of breast cancer in postmenopausal women. Now a longer-term study of the problem shows the higher risk of breast cancer continues among women who took hormones but stopped, that the cancer in these women may be more advanced and that the likelihood of dying of breast cancer is increased.

The link between hormone therapy and breast cancer was confirmed with the conclusion of the Women's Health Initiative study in 2005, based on about 5 1/2 years of data. However, researchers at the Los Angeles Biomedical Research Institute obtained consent from more than 12,000 of the women enrolled in the study to continue to follow them for breast cancer incidence.

With an average of 11 years of follow-up data, the researchers, led by Dr. Rowan T. Chlebowski, found 385 cases of invasive breast cancer in women who took estrogen-plus-progestin hormone therapy during the study compared to 293 cases of women who were in the placebo group and took no hormones. Moreover, among all of the women who developed breast cancer, those who took hormones were more likely to have positive lymph nodes -- an indication that the cancer has spread -- compared with the women in the placebo group and were more likely to die of the disease.

The Women's Health Initiative, however, studied older postmenopausal women, and questions linger today about whether hormone therapy might benefit younger menopausal or peri-menopausal women without increasing the risks of other disorders, such as breast cancer. As of now, doctors recommend hormone therapy only for women who have severe menopausal symptoms -- such as hot flashes -- and only for a year or two. But a study on whether even one or two years of hormone therapy increases the risk of breast cancer is needed, Dr. Peter B. Bach, of Memorial Sloan-Kettering Cancer Center, in New York, said in an editorial accompanying the study. "Clinicians who prescribe brief courses of hormone therapy for relief of menopausal symptoms should be aware that this approach has not been proven in rigorous clinical trials and that the downstream negative consequences for their patients are of uncertain magnitude," he wrote.

The study was published Tuesday in the Journal of the American Medical Assn.

-- Shari Roan / Los Angeles Times

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[For the record, 3:31 p.m., Oct. 19: An earlier version of this post said the researchers were from Harbor-UCLA Medical Center. They are from the Los Angeles Biomedical Research Institute, which is on the campus of Harbor-UCLA Medical Center.]

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