Overall, survival rates were 85.4 percent in the bone-drug group and 83.1 percent in the standard therapy group. In each group, 77 percent had disease-free survival.
But among the Zometa users, they reported 17 cases of osteonecrosis of the jaw, a severe disease that can cause the death of jawbone tissue. Another nine women were thought to have the condition. No one in the control group developed it.
While the results suggest routine use of Zometa for women with breast cancer is not advised, the researchers said Zometa might still be of some benefit for breast cancer patients who are more than five years past menopause.
Among this group were 519 women on the bone drug and 522 on standard therapy alone. At the five-year follow up, 78.2 percent of the bone drug group were alive and free of invasive recurrence, compared to 71 percent of the standard therapy group.
"The study is probably telling us that the interaction of reproductive hormones and bone is very important in driving recurrence of breast cancer," Coleman said.
The study was funded by Novartis AG, which makes the drug, and the National Cancer Research Network. Coleman has reported speaker fees from Novartis.
Dr. Otis Brawley, chief medical officer of the American Cancer Society, commented on the overall findings. "We had hoped that zoledronic acid would harden bone and reduce the rate of metastatic disease," he said. "We had also hoped this would increase survival. Neither occurred."
The increased risk of osteonecrosis is a concern, Brawley said. Even so, doctors must still pay attention to the prevention and treatment of osteoporosis in all cancer patients, he said.
To learn more about breast cancer, visit the American Cancer Society.<
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