U.S. Breast Cancer Cases Sharply Declined in 2003
Report says 6.7 percent decline may be linked to 2002 Women's Health Initiative findings
WEDNESDAY, April 18 (HealthDay News) -- Breast cancer incidence in the United States declined sharply in 2003, possibly because many postmenopausal women stopped using hormone-replacement therapy after the 2002 Women's Health Initiative study found it increased the risk of heart disease and breast cancer. The findings are published in the April 19 issue of the New England Journal of Medicine.
Peter M. Ravdin, Ph.D., M.D., of the M.D. Anderson Cancer Center in Houston, and colleagues analyzed data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) registries.
The researchers found that the age-adjusted incidence rate of breast cancer decreased by 6.7 percent in 2003 and leveled off in 2004. They also found that the drop applied only to women age 50 or older and was more common for estrogen-receptor-positive cancers than for estrogen-receptor-negative cancers. According to their regression analysis, the decrease began in mid-2002, and began to level off by mid-2003
"We believe that the data are most consistent with a direct effect of hormone-replacement therapy on preclinical disease, but this conclusion does not rule out some contribution from changes in screening mammography," the authors wrote. "In any case, attempts to understand the rapid reduction in incidence using theoretical models of breast cancer evolution and the effects of screening and treatment-- such as those of the National Cancer Institute's Cancer Intervention and Surveillance Modeling Network -- may lead to new insights into the development and prevention of breast cancer."