The United States saw a 7- percent decrease in breast cancer rates in 2003 after millions of women stopped taking hormone drugs for symptoms of menopause, researchers said.

Scientists said since more and more women refused to take hormone drugs for symptoms of menopause, the risk of developing breast cancer has been reduced.

The drug was believed to be linked with most cases of breast cancer.

The decline was the largest since 1990, said researchers in a study published by the Los Angeles Times on Friday.

The study found that 14,000 fewer women were diagnosed with breast cancer in 2003 than in 2002. More than 200,000 cases of breast cancer are diagnosed each year.

Though the study doesn't prove a causal link between the drop in hormone usage and the slide in breast cancer rates, it is the only plausible explanation, said co-author Dr. Rowan Chlebowski of the Los Angeles Biomedical Research Institute at the Medical Center of the University of California in Los Angeles.

There was a 1 percent drop in mammograms in 2003, which might mean fewer diagnoses but would not account for the large decline in cancer rates, he said.

"To have this kind of drop in cancer rates you need something very big to explain it," he said." After years of trying to defeat breast cancer by reducing it once it has occurred, it was a revelation to think that maybe there's an opportunity to decrease the risk of getting cancer to begin with," Chlebowski said.

The results are in line with a recent study that found the incidence of breast cancer among patients in Kaiser Permanente's Northern California region fell 10 percent from 2001 to 2003 while use of hormone replacement therapy dropped 68.

Taken together, the studies provide "strong supporting evidence " of the link between hormone therapy and breast cancer, said Lisa J. Herrinton, a Kaiser Permanente epidemiologist and co-author of the earlier study.

Prescriptions for the hormones estrogen and progestin fell by almost half after government researchers concluded in mid-2002 that hormone replacement therapy increased the risk of breast cancer in post-menopausal women.

Though researchers hailed the news, some cautioned that it was still too early to tell whether the downward trend would continue.

Julia Smith of the New York University Cancer Institute, who was not involved in the research, said undetectable tumors could still be present only to surface in the future.

"We may have slowed their growth trajectory so that if we don't see them this year, we may see them next year or in subsequent years," she said. "We have to reserve judgment."

Source: Xinhua