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Study: Stopping combined hormone therapy slows breast-cancer rates

Findings published by Center researchers and Women's Health Initiative colleagues support link between declining breast-cancer rates and combined hormone replacement therapy use in the United States

March 2, 2009
Drs. Ross Prentice and Garnet Anderson

co-authored a WHI follow-up study that supports the hypothesis linking a reduction in combined hormone replacement therapy and breast-cancer incidence in the United States.

Photo by Dean Forbes

Drs. Ross Prentice and Garnet Anderson are among the authors of a follow-up study from the Women's Health Initiative that supports the hypothesis that the recent reduction in U.S. breast-cancer incidence is predominantly related to a decrease in the use of combined estrogen plus progestin. The study appeared Feb. 5 in the New England Journal of Medicine.

When the Women's Health Initiative in 2002 halted its clinical trial of combined hormone therapy because the health risks, including increased breast-cancer risk, outweighed the benefits of HRT for managing menopausal symptoms, the incidence of breast cancer in the U.S. also quickly dropped. This suggested a cause-and-effect relationship between stopping HRT and decreased breast-cancer risk. However, this hypothesis was controversial. Some thought the decrease in breast cancer was too rapid to be a real effect, while others hypothesized that the decline may instead be attributed to a reduction in mammography rates during the same period.

Co-authors Prentice and Anderson are principal investigators of the Women's Health Initiative Clinical Coordinating Center, which is based in the Center's Public Health Sciences Division. 

The lead/corresponding author of the paper, "Breast Cancer After Use of Estrogen Plus Progestin in Postmenopausal Women," is Dr. Rowan Chlebowski, a professor of medicine at the University of California at Los Angeles.


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