US drop in breast cancer linked to reduced hormone useApr 18, 2007 | AFP
The research, based on data from the National Cancer Institute, shows that the breast cancer incidence rates in women in the United States fell 6.7 percent in 2003 from the previous year and have since stabilized.
The drop corresponds with a rapid decline in prescriptions for hormone replacement therapy (HRT) at the time following headline-grabbing reports that post-menopausal women who were using HRT that included both estrogen and progestin showed increased risks of breast cancer, heart disease and stroke.
The number of prescriptions written for the two most commonly prescribed forms of HRT in the United States plunged from 61 million in 2001 to 21 million in 2004, the study's authors reported in the April 19 issue of the New England Journal of Medicine.
According to the research team led by Donald Berry of the University of Texas, the decline in breast cancer incidence began in mid-2002 and leveled off after 2003.
The researchers, comparing breast cancer rates from 2001 and 2004, found a decrease in annual incidence of 8.6 percent.
The decrease only occurred in women over 50 and were more pronounced in women with cancerous tumors that were dependent on estrogen to grow and multiply, they said.
Of other risk factors the researchers considered including rates of mammography screening and changes in diet HRT was the only risk factor that changed markedly from 2002 to 2003 "and provides a possible explanation for this trend," the National Cancer Institute said in a statement.
"The speed at which breast cancer rates declined after the Women's Health Iniatiative announcements may indicate that extremely small ER-positive breast cancers may have stopped progressing, or even regressed after HRT was stopped," the institute, a part of the National Institutes of Health, said.
The head of the institute, John Niederhuber, recalled that breast cancer is the most frequently diagnosed cancer among women in the United States but all its causes remain unknown.
"Breast cancer rates had been increasing for two decades up to 2002. Finding the simple ways, such as limiting HRT use to decrease breast cancer risk, is a step forward," Niederhuber said in the statement.