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Some mystery behind decline in breast cancer

December 7, 2009 |  4:15 pm

MammographyMedical experts have attributed a recent decline in breast cancer rates among U.S. women to a slide in the popularity of hormone replacement therapy. But not so fast, says one researcher. The 7% drop in rates between 2002 and 2003 appears to be due to less use of hormone therapy and at least one other, unknown factor, said Bryan Sprague of the University of Wisconsin.

Hormone therapy is associated with an increased risk of breast cancer. This discovery, in 2002, led to a big drop in the number of women using the drugs. The timing of this drop corresponds to the drop in breast cancer rates. But Sprague, who presented his research today at a meeting in Houston of the American Assn. for Cancer Research, used estimates of the change in the prevalence of hormone use and the relative risk associated with hormone use and found that about 3% of the decline in cancer rates can be attributed to cessation of hormone therapy.

"So there's another 4% that is being caused by something we do not yet know," Sprague said in a news release. "This does not mean that women should start taking hormones again, but there appear to be additional factors that have contributed to the decline in breast cancer."

-- Shari Roan

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