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Study: Drug Used to Protect Bone May Also Prevent Breast Cancer Recurrence (dateline July 29, 2008)

The drug Zometa (generic name, zoledronic acid) is used to treat bone loss in cancer patients, but a new study finds that it may also help prevent the recurrence of breast cancer. In a study released at the annual meeting of the American Society of Clinical Oncology, researchers announced that early-stage breast cancer patients who received Zometa, along with hormone therapy, reduced their risk of a breast cancer recurrence by 35% compared to women who were treated with hormone therapy and not Zometa. The researchers caution that further study is needed to confirm the findings and determine which patients are most likely to benefit from Zometa.

Zometa belongs to a class of drugs called bisphosphonates. It is approved by the U.S. Food and Drug Administration (FDA) to treat complications from bone metastases-cancer that has spread from another site (such as the breast, lung, or liver) to the bone. When breast cancer spreads past the breast and axillary (armpit) lymph nodes, for example, it often spreads first to the bone. As advanced breast cancer dissolves portions of bone, a variety of problems can occur. Bone metastases can cause pain, decreased physical activity, and potentially severe problems such as fractures.

To determine whether Zometa could reduce the risk of a recurrence of breast cancer, Michael Gnant, MD, Professor of Surgery at the Medical University of Vienna and President of the Austrian Breast and Colorectal Cancer Study Group, and colleagues studied 1800 pre-menopausal women with early-stage breast cancer. The women were treated with treated with surgery, ovarian suppression (drugs that stop the production of hormones by the ovaries), and hormone therapy. Hormone therapy is commonly used to treat a type of breast cancer that is hormone-receptor positive. This type of cancer depends on estrogen for survival. Examples of hormone therapies includes the drugs tamoxifen and Arimidex (generic name, anastrozole).

In the study, the researchers compared women who received hormone therapy with Zometa and those who received hormone therapy without Zometa. Those who received Zometa did so as a six-month injection and did not experience any unusual side effects, according to the researchers.

The results showed that after about five years, women treated with hormone therapy (either tamoxifen or Arimidex) and Zometa reduced their risk of a breast cancer recurrence by 35% compared with women who received hormone therapy alone. Among women who received Zometa, 6% died or experienced a recurrence of breast cancer compared to 9% of women who did not receive Zometa.

It's very exciting to find that in addition to preventing bone loss in women receiving hormone therapy for breast cancer, [Zometa] can also reduce the likelihood that breast cancer will return in some women," said Dr. Gnant, in a statement on the American Society of Clinical Oncology website.

The researchers are uncertain how Zometa works to prevent breast cancer in some women. They suspect that the drug may help strengthen the immune system but did not investigate this during the study. According to Dr. Gnant, "future research will focus on developing the appropriate treatment schedule and determining which women will benefit the most from this treatment."

It is important to note that Armidex is currently FDA-approved only for post-menopausal women. However, pre-menopausal women were allowed to take the drug during the study because they were underoing ovarian suppression.

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