Breast Cancer Drop Tied To Less Hormone Use

Some researchers, however, questioned the findings, saying the drop in breast cancer occurred too soon to have been caused by the decline in hormone use.

"Even if there was a cause and effect, you wouldn't expect it to show up for five or 10 years," said Hugh Taylor of Yale University. "It just doesn't fit with what we know about the basic biology of breast cancer."

Wyeth Pharmaceuticals, which makes the most widely prescribed hormones, also questioned the link, saying hormone use continued to fall while the breast cancer rate remained stable after the initial drop. The researchers, they said, had failed to rule out other causes, such as a decline in mammogram use.

"We do respectfully disagree with the conclusion here," said Joseph Camardo, Wyeth's senior vice president of global medical affairs.

Millions of women took hormones for years to alleviate hot flashes and other symptoms of menopause. Some also viewed hormones as a virtual fountain of youth -- boosting energy, preventing wrinkles and providing health benefits, including reducing the risk of heart disease.

In 2002, however, the large federal Women's Health Initiative study stunned doctors and patients when it showed that the hormones not only failed to protect women's hearts, they appeared to increase the risk of heart attacks and strokes, as well as breast cancer and other health problems. The news prompted millions of women to abandon the drugs.

Researchers first reported last year that the breast cancer rate had dropped in 2003 after rising steadily since the 1980s, and that the drop appeared to coincide with the news about hormones. Experts have been waiting for the latest federal data, from 2004, to see if the trend persisted.

The new analysis showed that the breast cancer rate began falling almost immediately after the Women's Health Initiative findings were released in July 2002, dropping 6.7 percent between 2002 and 2003. The 2004 data showed that the rate remained at the lower level, having fallen 8.6 percent between 2001 and 2004.

The researchers said that indicates the drop was primarily caused by the decrease in hormone use and not other factors, such as fewer women having mammograms, greater use of hormone-blocking drugs such as tamoxifen or an unknown change in the environment, and that it will be long-lasting.

"The fact that the incidence rate did not go back up suggests that the effects will be long-lived," said Peter Ravdin of the University of Texas, who helped conduct the analysis.

The link is strengthened by the fact that the decline occurred primarily in women ages 50 to 69, the age group most likely to use hormones, and predominantly in a form of breast cancer sensitive to estrogen. New cases of this type fell 14.7 percent, the researchers said.

The researchers and others emphasized that further research will be needed to determine whether the reduction in diagnoses will translate into fewer deaths.

Researchers suspect hormone use may spur the growth of tumors that may never become life-threatening. Without hormone use, the tumors may remain small enough to never be detected by mammograms. They may even shrink.

"Think of a cancer that you are feeding with hormones and now you stop the fuel. What's going to happen to it?" Berry said. "Most likely it stops growing and stays under the radar, or maybe even regresses. It could even disappear."