Researchers present Thursday at the annual San Antonio Breast Cancer Symposium in San Antonio noted that Swiss-based Novartis AG’s bone drug Zometa (zoledronic acid) also fights breast cancer. More exactly women treated with the drug had greater tumor shrinkage and were less likely to undergo mastectomies than women who followed only chemo.

Robert Coleman, MD, professor of medical oncology at the University of Sheffield in England and colleagues tested the drug on 205 women with breast cancer. Half of them were given chemo and half were given chemo plus Zometa once every three to four weeks for six months before breast cancer surgery.

Zometa belongs to a group of drugs called bisphosphonates, which are thought to stimulate cancer-fighting immune cells, choke the growth of blood vessels that feed tumors and cause cancer cells to self-destruct. The drug is already approved to treat breast cancer that has spread to the bone and, earlier this year, was reported to lower the risk of breast cancer recurrence in pre-menopausal women with early estrogen- or progesterone-positive tumors. Side effects of the drug include bone, joint or muscle pain and in rare cases, jawbone decay. Bisphosphonates are mainly used to treat osteoporosis.

Women in the Zometa group had their tumors shrunk to 20.5 millimeters in size compared with 30 millimeters in the control group. “And even after the analysis took into account other factors that can affect tumor size (such as whether the tumor is fueled by hormones), there was still a better response with Zometa,” Coleman said. Also women given Zometa were less likely to need their whole breast removed versus just the lump. To be more specific, 65 percent of Zometa women underwent a mastectomy compared with 78 percent of those who received chemo.

Eleven percent of these women had a complete response to treatment (no evidence of cancer in their breast or lymph nodes) compared with 6 percent of the other women.

Now specialists in cancer are eagerly awaiting the results of a second, ongoing study testing Zometa in 3,360 women who had breast cancer after menopause. After menopause, women have a higher chance of developing breast cancer. If the results of this trial are as encouraging as those released at the conference, “it would mean fewer patients would have to have mastectomies,” Coleman said. However, he added that this is not overnight going to change the management of women with breast cancer.

According to the World Health Organization, breast cancer is the fifth cause of death worldwide, with 548,000 deaths in 2007. It is also the most common form of cancer in women. About 182,000 women in the US will be diagnosed with breast cancer in 2008, the American Cancer Society estimates.