A rapid decline in the use of hormone drugs in 2002 probably explains the drop in breast cancer cases in recent years, according to a University of California study.
The findings also suggest that women who stop taking hormone drugs may be able to reduce their risk of breast cancer quickly, researchers said. The study, by researchers from the University of California, San Francisco, is published online in today's Journal of the National Cancer Institute.
Millions of menopausal women stopped taking hormone replacement drugs, used to treat symptoms such as hot flashes, after a study linked Wyeth's Prempro to heart disease and cancer. Hormone drugs contain estrogen, which is implicated in breast cancer risk. The University of California study found annual rates of estrogen-fueled cancers fell 13 percent a year from 2001 to 2003, while overall breast cancer rates fell 5 percent.
"There is clearly a causal link," said Karla Kerlikowske, professor of medicine at the University of California in San Francisco and the studies lead author. "For people who stop taking hormones, their risk decreases fairly quickly. That's a positive, exciting message."
The study adds to similar findings published in April by a group from University of Texas M.D. Anderson Cancer Center in Houston, which showed a 6.7 percent decline in the number of women diagnosed with breast cancer in 2003.
The University of California study found that use of hormone therapy declined 7 percent a year from 2000 to 2002 and then plunged 34 percent from 2002 to 2003.