Study: Combination Hormone Therapy Greatly Ups Breast Cancer Risk

Women who take hormone replacement therapy after menopause face a greater risk of breast cancer than had been thought, especially if they take a combination of estrogen and progestin, according to Britain's "Million Women Study."

The findings, reported in the journal The Lancet, add to compelling evidence from U.S. studies that the risks of invasive breast cancer from combination hormone therapy were greater than many doctors had predicted.

The British study concluded that women taking hormone replacement therapy had a 22 percent higher risk of death from breast cancer compared to women not receiving therapy.

The researchers found that women taking any hormones -- whether estrogen alone or in combination with progestin, and whether in pills, patches or gels -- were significantly more likely to develop breast cancer than those who do not, and the risk goes up the longer they take the drugs.

The greatest risk, however, was for women taking any combination of estrogen and progestin, which the researchers said doubles the risk for breast cancer. Women taking estrogen alone are 30 percent more likely to get breast cancer compared with nonusers.

The results dealt another huge blow to the reputation of the drugs, once used by millions of women to treat the symptoms of menopause, such as hot flashes and night sweats.

But in the past two years, researchers increasingly have questioned whether the long-term benefits of hormone replacement therapy outweighed risks.

"What we've shown is this huge, huge, highly significant increase in risk," said Valerie Beral, a professor of epidemiology at the University of Oxford. "We've really confirmed in an unequivocal way that estrogen and progestin combined has a much greater risk of breast cancer."

Other Sources: The Lancet