In 2000, only about 0.2 percent of U.S. women aged 40 to 79 took tamoxifen to prevent breast cancer. In 2005, the prevalence was even lower -- only 0.08 percent.
The data did not say specifically how many of the women taking tamoxifen were at high risk for breast tumors, said Andrew N. Freedman, senior author of the paper appearing in the February issue of Cancer Epidemiology, Biomarkers & Prevention, but "we probably could assume they were high-risk."
The authors could only speculate on why the numbers were so low.
"It may be that patients and their physicians do not think the benefits outweigh the risks. It could be that physicians are not getting education about use of the drug. It could be concerns about side effects or physicians reluctant to prescribe," said Freedman, who is chief of the clinical and translational epidemiology branch of the division of cancer control and population sciences at the U.S. National Cancer Institute.
One recent study found that worries about side effects are a major reason why high-risk women are unwilling to take tamoxifen.
Tamoxifen's side effects include hot flashes, endometrial cancer and blood clots. A newer agent, raloxifene (Evista), a sister drug to tamoxifen, might be an alternative for women concerned about the risk of endometrial cancer.
However, tamoxifen works for both invasive and noninvasive breast cancer while raloxifene works only for the former, Brooks said.
Also tamoxifen, said Jordan, "is the only game in town for premenopausal women."
In the end, though, the decision lies with each individual woman.
"I think that the use of tamoxifen for chemoprevention is something that is a very personal choice between the physician and patient, and de
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