Tamoxifen is used to reduce the incidence of breast cancer in healthy women at high risk of developing the disease, but researchers suspected it may be useful in other ways. "Tamoxifen has mixed effects depending on the organ it?s acting on. Therefore, it?s important to determine the drug?s effects on other organs such as the heart and blood vessels, because cardiovascular disease is much more common than breast cancer," says Mary Cushman, MD, MSc, lead author of the study and Assistant Professor of Medicine at the University of Vermont in Burlington.

Cushman said further study is needed among a broader sampling of women and cautioned that no direct benefit to the heart has been firmly established -- but she believes the results of this research may be good news for individuals taking tamoxifen. "Taken together with previous studies, this data suggests potential that tamoxifen might be beneficial in terms of reducing heart disease risk," she says. Heart disease is the number one killer of American women.

According to the study, tamoxifen may reduce the amount of two proteins called "inflammatory markers." Previous studies have shown that both proteins present in high levels could indicate an increased risk for heart disease. Tamoxifen was shown to reduce one marker protein, called C-reactive protein (CRP), by 26%. The other marker, fibrinogen, which is in blood plasma and is essential for blood coagulation, was reduced by 22%. The effect on fibrinogen was higher in women with higher baseline cholesterol.

Previous breast cancer trials have reported a 15% to 60% reduction in death from heart disease in women treated with tamoxifen, and researchers assumed the reduction was due to the drug?s tendency to reduce cholesterol. The impact on the two proteins, however, may signal even more benefits from taking tamoxifen. Women in this study, in fact, had a 9% reduction in total cholesterol levels.

The study participants were 111 healthy women who were participating in a breast cancer prevention trial. The average age of the women was 58, and most were postmenopausal. Every day for six months, 51 women took 20-milligram tamoxifen pills, and 60 took placebo pills. At the end of study, the research team compared CRP, fibrinogen, and cholesterol levels between the tamoxifen and placebo groups.

Researchers suggest it is possible that women at risk for breast cancer might differ from other women in their biomarker responses. They say that further study on the effects of tamoxifen should include a larger number and broader categories of women. In this study, all the participants were white women at low risk for heart disease.

Ralph Vogler, MD, American Cancer Society scientific program director, agrees that more research could reveal why tamoxifen has these apparently beneficial results. "Most of the data indicates that tamoxifen does suggest a reduction of cardiovascular events. What is not clear is the mechanism of how that is accomplished," he says.