Bone-building drugs such as Fosamax and Actonel might help prevent breast cancer, according to two new studies presented Thursday at a medical symposium in Texas. The studies suggest that women who take the drugs, called bisphosphonates, are about one-third less likely to develop breast cancer than women who do not.

In one U.S. study, scientists found there were 31 percent fewer cases of breast cancer among women who took Fosamax or other oral bisphosphonates than among women who didn’t. Other commonly used oral bisphosphonates are Boniva and Actonel.

In the other study, researchers in Israel found that women who had used bone-building drugs, mostly Fosamax, were 29 percent less likely to develop breast cancer. The two studies used different methods to arrive at the same basic result, adding to the strength of the findings, Indiana University’s Theresa Guise said at a news briefing on the findings at the Breast Cancer Symposium in San Antonio, Texas. The studies do not prove that the drugs prevent breast cancer, doctors say. More definitive studies will be done in the next one or two years to give a clearer picture about the effectiveness of the drugs in preventing breast cancer. Until then, women should only take these drugs if they have osteoporosis or other bone problems, they say.

However, Rowan Chlebowski, a medical oncologist who headed the U.S. study, said that “the idea that bisphosphonates may protect against breast cancer incidence is very exciting because there are about 30 million prescriptions for them written annually in the United States.” “By protecting their bone health, women may also be protecting themselves against cancer,” he said.

The U.S. study involved more than 150,000 women in the Women’s Health Initiative, a study known for revealing previously unrecognized risks from taking estrogen and progestin pills after menopause. The second study tracked more than 4,000 postmenopausal women in Israel.

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