..Bone-building drugs used by tens of millions of women to fight osteoporosis also cut the risk of breast cancer, suggesting the drugs may play a dual role in keeping women healthy.

"Bone loss and potential fractures are a known complication of breast cancer therapy. Our feeling is that bisphosphonates may actually prevent disease recurrence through a variety of mechanisms," said Dr. Adam Brufsky, associate director of clinical investigation at the University of Pittsburgh Cancer Institute.

Brufsky authored one of several studies exploring the role of bone-building drugs in breast cancer prevention that were to be presented Thursday at the San Antonio Breast Cancer Symposium.

Bisphosphonates are already used to treat complications that result from breast cancer spreading to the bones.

One study looked at more than 150,000 postmenopausal women who participated in the U.S. government-led Women's Health Initiative (WHI).

The women taking bisphosphonates, namely Fosamax (alendronate), had a 32 percent reduction in their rate of invasive breast cancer compared to women who were not taking one of these drugs.

The University of California, Los Angeles, researchers were able to control for the fact that women with low bone mineral density are already at lower risk for breast cancer.

Because the study was not a randomized, controlled one, said lead investigator Dr. Rowan Chlebowski, a professor and medical oncologist with UCLA, "the findings are not definitive but they do provide a strong signal."

In another study, Israeli researchers found that postmenopausal women taking bisphosphonates for one or more years had a 29 percent reduction in their risk of breast cancer.

And the tumors that did appear tended to be estrogen receptor-positive and thus easier to treat than estrogen receptor-negative tumors.

And in other news from the symposium:

Researchers from the University of Pittsburgh Cancer Institute, led by Brufsky, concluded that zoledronic acid, another bisphosphonate, is safe and effective for use by postmenopausal women with breast cancer who are being treated with aromatase inhibitors. Bone mineral density increased 6.2 percent in women taking zoledronic acid, compared with 2.4 percent in the control group. Fractures were also reduced slightly in the treatment group, but it's unclear how significant this was. Zoledronic acid is marketed under several brand names, including Zometa.
A new drug, denosumab, a monoclonal antibody, performed better than zoledronic acid in easing problems associated with the spread of breast cancer to the bones.
A final study found that it was safe to give zoledronic acid to women with breast cancer being treated with the aromatase inhibitor Femara (letrozole) before surgery.

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