Study: Hormone therapy caused breast cancer for thousands

By Anne Harding

Health

U.S. breast cancer cases have dropped in women aged 50 to 69 in recent years because many women have stopped taking hormone therapy, according to a study in The New England Journal of Medicine.

A study in the New England Journal of Medicine suggests long-term use of hormone therapy causes breast cancer.

The report is the best evidence to date that the breast cancer drop is indeed due to a decline in hormone use, rather than changing rates of mammograms or other factors, experts said.

The good news: The study found that breast cancer risk in women who took hormones dropped back down to normal soon after they quit.

The bad news: In the last decade in which it was still widely used (1992--2002), long-term hormone therapy probably caused breast cancer in 200,000 women, said Dr. Rowan T. Chlebowski, a medical oncologist at the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance and the study's lead author.

Currently, the Food and Drug Administration recommends that women who want to take hormones only do so at the lowest dose and for the shortest possible time to relieve menopausal symptoms, such as hot flashes. Using hormones for two years or less appears to be safe for many women, and estrogen alone is generally safer than estrogen-progestin, according to a recent analysis by experts at the American Cancer Society. Health.com: Hot flash triggers-- how to avoid them

Long-term hormone use, however, is a problem. Scientists who study cancer rates saw a 10 percent drop-off in new breast cancers in 2003, about a year after alarming findings from the Women's Health Initiative (WHI) study led many older women to stop taking estrogen and progestin. Only women who've had a hysterectomy can take estrogen alone; progestin is added to estrogen to reduce the risk of cancer of the lining of the uterus.

In 2003, as well as in 2004 and 2005, 20,000 fewer breast cancer cases were diagnosed in the United States than would have been expected. Read more...