Breast cancer decline attributed to drop in HRT

By Will Boggs, MDFri Aug 24, 5:29 PM ET
Invasive breast cancer rates have fallen since the substantial decline in postmenopausal hormone replacement therapy (HRT) occurred, even after a decline in breast cancer screening rates, according to findings published in the 5th Journal of the National Cancer Institute.
"It's encouraging that breast cancer rates decreased with decreases in use of hormone therapy," Dr. Karla Kerlikowske told Reuters Health. This implies that women who stopped using hormone therapy in a relatively short period of time have a risk of breast cancer similar to women who have never used hormone therapy."
Kerlikowske from San Francisco Veterans Affairs Medical Center and the University of California, San Francisco, and colleagues examined whether parallel declines in postmenopausal HRT use and rates of breast cancer are present among women undergoing routine screening mammography.
They point out that the breast cancer detection rate is higher in women undergoing mammography, so "the proportion of women in the population undergoing routine screening mammography will influence population-based estimates of breast cancer incidence."
The prevalence of postmenopausal HRT use started to decline about the same time that observational studies in early 2000 linked use of estrogen and progestin combinations to greater breast cancer risk than use of estrogen alone. An even greater decline followed the release of the Women's Health Initiative study in 2002.
The current study involved over 600,000 screening mammograms on women 50-69 years of age, of whom 3238 were diagnosed with breast cancer. The rate of estrogen receptor-positive invasive cancer was stable until 2001, but declined 13 percent per year from 2001 to 2003, the report indicates. Rates of estrogen receptor-negative invasive cancer did not change during this interval.
"Our results suggest that a decline in postmenopausal HRT use has contributed to the decline in breast cancer incidence in the United States," the investigators conclude. "The small decline in screening mammography observed in the United States is unlikely to explain the national declines in breast cancer incidence."
"For those women who need to take estrogen and progestin to control hot flush symptoms, they should be encouraged to take the medication for as short a time as possible," Kerlikowske emphasized.
"We are monitoring women who discontinue postmenopausal hormone therapy to determine if their screening mammography utilization changes, and to measure their risk of breast cancer over time compared to never-users of hormone therapy," Kerlikowske added.
SOURCE: Journal of the National Cancer Institute, September 5, 2007.