Hormone Therapy Linked to Higher Breast Cancer Death Risk

October 19, 2010— -- New evidence today adds to the belief that hormone replacement therapy may do more harm than good for many women after menopause, and it has many experts trying to figure out for which women the therapy is safe.

New results released Tuesday from the ongoing Women's Health Initiative trial found that not only do postmenopausal women who take a combination of estrogen and progestin therapy have a higher chance of getting aggressive forms of breast cancer, but that they may be at higher risk of dying from the disease.

The results, from an 11-year follow up with more than 12,000 women who were randomly assigned to receive either the combination hormone therapy or a placebo, found 385 women taking the therapy developed an aggressive form of breast cancer, compared to 293 in the placebo group. Twenty-five women who took hormone therapy died from breast cancer during the study, compared to 12 women in the placebo group.

"It is early in the follow-up and the number of breast cancer deaths will certainly substantially increase as we move forward," said Dr. Rowan Chlebowski, professor of medicine at the David Geffen School of Medicine at the University of California, Los Angeles, and lead author of the study.

Women in the study who used estrogen and progestin for five-and-a-half years -- which is considered long-term use of the therapy -- were at higher risk of getting breast cancer, said Chlebowksi.

Earlier results of this trial indicated a connection between synthetic hormone therapy -- commonly marketed as as the drug Prempro -- and less aggressive forms of breast cancer. But results now suggest that women who took hormones may be at risk of any, including more aggressive and late-stage, forms of breast cancer.

"For women currently on HRT, I think it warrants a significant talk with their physician as to whether they warrant the therapy," said Dr. Jennifer Litton, assistant professor of breast oncology at MD Anderson Cancer Center in Houston.

Hormone replacement therapy includes medications containing female hormones to replace the ones the body no longer makes after menopause. Although the FDA has only approved hormone replacement therapy to reduce the risk of osteoporosis in postmenopausal women and prevent hot flashes, the medication is also likely to be prescribed off-label to control groups of symptoms such as mood swings, and dryness.

While experts said diet and exercise often curb these symptoms, hormone therapy is prescribed for women with severe symptoms.

"For some women, these symptoms are so severe that it's life-altering," said Litton.