Bone drugs may help prevent breast cancer

New results from a landmark women's health study raise the exciting possibility that bone-building drugs such as Fosamax and Actonel may help prevent breast cancer.

Women who already were using these medicines when the study began were about one-third less likely to develop invasive breast cancer over the next seven years than women not taking such pills.

The study is not enough to prove that these drugs, called bisphosphonates, prevent cancer. More definitive studies should give a clearer answer in a year or two.

Yet it greatly amplifies the hopeful buzz that started last year when researchers reported that a bisphosphonate cut the chances that cancer would come back in women already treated for the disease.

"Now we're actually looking at this in the general population - healthy women who have never had breast cancer. And it looks like it's protective in those women as well," said Dr. Peter Ravdin of the University of Texas Health Science Center at San Antonio.

Millions of women already take bisphosphonates for bone-thinning osteoporosis, or to prevent fractures from cancer that has spread to their bones.

Of the 151,592 participants in the study, 2,216 were taking bisphosphonates - mostly Fosamax - when the study began. About seven years later, 31 percent fewer invasive breast cancer cases had occurred among those women than the others, Dr. Rowan Chlebowski of Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, Calif. found.

However, women taking bisphosphonates were more likely to develop a noninvasive tumor of the milk duct called DCIS. Chlebowski contends this is an acceptable trade-off: For every 1,000 women taking a bisphosphonate for one year, one fewer case of invasive, life-threatening breast cancer would occur.

The study did not collect information on side effects. Bisphosphonates can cause bone, joint or muscle pain and in rare cases, jawbone decay.