Zometa, given as an infusion, is a member of a class of drugs called bisphosphonates that help maintain bone strength.
Animal and lab research suggests that bisphosphonates may fight breast cancer in a number of ways -- by directly killing tumor cells, by cutting off their blood supply, or by stimulating the immune system to mount an attack against the tumor, says Rowan Chlebowski, MD, PhD, a medical oncologist at Harbor-University of California, Los Angeles Medical Center.
The new research builds on a study presented at the 2008 breast cancer meeting showing that Zometa appears to prevent breast cancer from coming back.
Then, last year, Chlebowski presented an analysis of data on more than 150,000 women that showed that there were 31% fewer cases of breast cancer among women who took bisphosphonate pills than among women who didn't.
Zometa Does Not Appear to Prevent Breast Cancer Relapses
The new five-year study involved 3,360 patients with breast cancer that had spread to the lymph nodes.
A total of 404 women given Zometa plus standard therapy and 403 of those given standard treatment alone had a recurrence, developed a new cancer, or died before they had a recurrence.
Altogether, 243 women on Zometa and 276 on standard treatment alone died, a difference so small it could be due to chance.
Twenty-six women on Zometa had confirmed or suspected cases of osteonecrosis of the jaw, a side effect of bisphosphonates that causes the jawbone to decay.
Routine Use of Zometa for Breast Cancer Treatment Not Warranted
Since only women who were well into menopause appeared to benefit from the drug, Coleman says he suspects it works best in an environment of little or no estrogen.
Commenting on the findings, Sharon Giordano, MD, MPH, of the University of Texas M.D. Anderson Cancer Center in Houston, says the scientific community has been waiting to hear these results.
The bottom line, she tells WebMD, is that the routine use of Zometa to prevent breast cancer recurrence is not warranted at this time.
As for its apparent benefit in postmenopausal women, Giordano says, "Those findings are very intriguing, but not definitive."
The results do not affect Zometa and other bisphosphonates' "important role in treating bone loss among women with breast cancer," Giordano says.
Zometa is approved for the reduction or delay of bone complications across a broad range of cancers that have spread to the bone and multiple myeloma. It costs about $1,000 an infusion.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.