SUNDAY, Sept. 25, 2011 (HealthDay News) -- The bone drug Zometa, once considered a promising weapon to reduce the risk of breast cancer recurrence, should not be used routinely in treatment of the disease, researchers say.
In a new study of breast cancer patients, Zometa (zoledronic acid) did not increase disease-free survival overall, and it appeared to raise the risk of a serious side effect, said study co-author Dr. Robert Coleman, a professor of medical oncology at the University of Sheffield in England.
However, "for the one-third of women in the study who had gone fully through menopause at the time of study entry, there is significant benefit in terms of both disease recurrence and overall survival," Coleman added.
The results of the trial, published online Sept. 25 in the New England Journal of Medicine, were slated to be presented Sunday at the 2011 European Multidisciplinary Cancer Congress in Stockholm. Coleman also presented findings from the study at the San Antonio Breast Cancer Symposium in late 2010.
Women receiving hormone therapy for breast cancer treatment are prone to weakening and thinning of the bone, a condition known as osteoporosis, so they often receive bone-building drugs known as bisphosphonates. Some previous research had suggested these bone drugs might also help to prevent recurrence of breast cancer.
Zometa, which is delivered intravenously, is also used to relieve pain when cancer spreads to the bone.
In the study, Coleman and his colleagues randomly assigned almost 3,400 patients with early-stage breast cancer to standard therapy or to standard therapy plus Zometa.
The research team looked at overall survival and disease recurrence for an average of nearly 5 years of follow-up. They found no significant differences between the groups. According to the study, 377 patients in the group receiving the bone drug either died or had a recurrence during the five-year study, compared to 375 in the standard therapy group.
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.