(Ivanhoe Newswire) -- Postmenopausal women may reduce their chances of developing breast cancer by taking raloxifene, no matter what their risk is for the disease.

Raloxifene is also known by the brand name Evista. Doctors use it to treat and prevent osteoporosis. The Food and Drug Administration has not approved it to prevent breast cancer.

A new study reveals raloxifene reduced the risk of breast cancer by 58 percent in women without a family history of the disease and by 89 percent in those with a history. The drug's protection seemed greatest in women who may be genetically predisposed to develop breast cancer, but researchers cannot explain why.

"It could be due to chance, or there may be other factors at work that we don't know about," reports lead author Marc E. Lippman, M.D., from the University of Michigan in Ann Arbor. "But our bottom-line analysis as to why raloxifene universally reduces the risk of developing invasive cancer in women without a family history is that it interferes with the duration and concentration of estrogen, which acts as a tumor promoter in the majority of breast cancers."

Researchers analyzed data from two large studies of raloxifene. One tested the ability of the drug to prevent fractures in 7,705 postmenopausal women with osteoporosis. The second studied the effect of raloxifene on breast cancer incidence in 4,011 of the original participants.

Women who have a higher risk of developing breast cancer are usually older and have had more exposure to estrogen. This new study found that to be true, but it also found raloxifene reduced the risk of breast cancer in both women at lower and higher risk of the disease.

SOURCE: Clinical Cancer Research, 2006;12:5242-5247