A drug used to strengthen the bones of women with breast cancer helped cut the risk of the cancer returning by 36 percent, European researchers said on Saturday,
They said Zometa, sold by Swiss drug giant Novartis AG, helped women with early-stage breast cancer who were already taking hormone therapy to reduce their cancer risk.
The finding comes from the first large-scale study to show a drug in the class known as bisphosphonates can reduce the risk that cancer will come back.
"I'm convinced it's going to change the landscape," said Dr. Michael Gnant of the University of Vienna, who presented his findings at a meeting of the American Society of Clinical Oncology in Chicago.
"In these patients, I would expect it is going to be pretty much the standard of care pretty soon," Gnant said in a telephone interview.
'Fueling the cancer'
Zometa, known generically as zoledronic acid, is usually prescribed to fortify the bones of breast cancer patients whose tumors have spread to the bone. Breast and other cancers commonly spread to the bone and patients can be crippled by the pain and fractures that result.
Gnant and colleagues studied 1,803 premenopausal women who were taking a synthetic hormone to shut down their ovaries, a practice more common in Europe than in the United States, where such women often get chemotherapy.
"The purpose is to reduce the estrogen levels that circulate in the body. That is what is fueling the cancer," Gnant said.
Women in the study then were given one of two types of anti-estrogen drugs — tamoxifen and AstraZeneca's newer estrogen-blocker anastrozole or Arimidex.
Arimidex is typically only given to post menopausal women, but the ovarian suppression therapy in effect made women in the study post-menopausal and the researchers wanted to see if this approach would have a benefit.
Researchers also gave the Zometa to prevent bone loss in these younger women. But the bisphosphonate appears to have interfered with the cancer as well, something that has been suggested in smaller studies.
"They can act as an anti-cancer drugs. This is the first trial to show they actually do," Gnant said.
The way Zometa reduces cancer risk is not clear. It may be inhibiting cancer cell growth or it may be preventing cancer cells from sticking to the targeted organ. It also could be several things at once, Gnant said.
The American Society of Clinical Oncology's Dr. Julie Gralow of the University of Washington said the findings do not easily translate to breast cancer care in the United States, where most women with early stage breast cancer undergo chemotherapy.
Nevertheless, the drug had very few side effects, and doctors will likely try it. "I think the U.S. will use it," she said in an interview.
Larger trials are under way that will give more evidence on the benefits of such bone drugs in inhibiting cancer. But Gralow said doctors likely will not wait before they start recommending the drug.
"It's a pretty benign therapy for reducing recurrences," she said.