Fewer breast cancers linked to less hormone therapy

(Reuters) - A sharp decline in new breast cancer cases in 2003 in the United States have come because millions of older women ceased hormone replacement therapy the previous year, researchers said on Thursday.

But they stressed that because their analysis is based on population statistics, the reasons are not completely certain.

"The investigators report that there was an overall 7 percent relative decline in breast cancer incidence between 2002 and 2003," the University of Texas M. D. Anderson Cancer Center said in a statement.

"The steepest decline—12 percent—occurred in women between ages 50-69 diagnosed with estrogen receptor positive (ER-positive) breast cancer," it said. These types of tumors are fueled by the hormone estrogen.

The study was presented at the 29th annual San Antonio Breast Cancer Symposium.

Researchers said that as many as 14,000 fewer women were diagnosed with the disease in 2003 than in 2002, a year in which there were an estimated 203,500 new U.S. cases.

"It is the largest single drop in breast cancer incidence within a single year I am aware of," said Dr. Peter Ravdin, a research professor in the Department of Biostatistics at M. D. Anderson.

"Something went right in 2003, and it seems that it was the decrease in the use of hormone therapy, but from the data we used we can only indirectly infer that is the case," he said in a statement.

HRT provides the hormone estrogen and sometimes also progestin to women after menopause.

But a big study in 2002 suggested that the combination of estrogen and progestin raised the risk of breast cancer. This brought a premature halt to a Women's Health Initiative study of more than 16,600 women between 50 and 79 who were using HRT, and caused widespread confusion

More analysis of the Women's Health Initiative also showed that HRT could raise the risk of heart disease and especially strokes, and HRT was abandoned except as a way to relieve the most debilitating and stressful symptoms of menopause, such as hot flashes and insomnia.

Ravdin said about 30 percent of American women over the age of 50 had been taking HRT in the early years of this decade but about half of the women stopped in the later part of 2002 after the results of this link were made public.

"Research has shown that ER-positive tumors will stop growing if they are deprived of the hormones, so it is possible that a significant decrease in breast cancer can be seen if so many women stopped using HRT," he said.

"It takes breast cancer a long time to develop, but here we are primarily talking about existing cancers that are fueled by hormones and that slow or stop their growing when a source of fuel is cut," added Donald Berry, an M.D. Anderson professor who helped lead the study.

"Incidence of breast cancer had been increasing in the 20 or so years prior to July 2002, and this increase was over and above the known role of screening mammography. HRT had been proposed as a possible factor, although the magnitude of any HRT effect was not known."