Breast Cancer Health Center

Bone-Building Drugs May Cut Breast Cancer Risk

Bisphosphonates and Breast Cancer Recurrence

The new research builds on a study presented at last year's breast cancer meeting showing that the intravenous bisphosphonate Zometa appears to prevent breast cancer from coming back.

Animal and lab research suggests that the drugs 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, Chlebowski says.

In fact, there's every reason to expect that the drugs may protect against other types of cancer as well, he says, adding that future study testing that hypothesis is planned.

Using Women's Health Initiative data, Chlebowski and colleagues researchers compared breast cancer rates in 2,816 women who reported using oral bisphosphonates at the start of the study with those of 151,592 women who said they did not take the drugs.

The women were followed for an average of 7.8 years. During that time, 5,156 of the women developed breast cancer, with 64 of the cases among bisphosphonates users.

After taking into account the women's bone mineral density, this translated to a 31% lower risk of cancer among bisphosphonates users.

"Since bisphosphonates are prescribed for women with low bone mineral density -- and low bone mineral density has been associated with lower breast cancer incidence -- it's important to correct for that," Chlebowski says.

Israeli Breast Cancer Study

The second study involved more than 4,000 women in Israel, about half of whom had breast cancer. Using pharmacy records, the researchers determined whether the women had taken bisphosphonates.

After taking into account a variety of risk factors for breast cancer including age, ethnicity, fruit consumption, sports activity, family history of breast cancer, and body mass index, women who took the drugs for over a year were 29% less likely to have breast cancer than women who did not.

Taking the drugs for longer didn't appear to offer any more protection than taking them for one year, the study showed.

"Importantly, the tumors that developed among bisphosphonates users were more likely to be estrogen-receptor-positive," says study head Gad Rennert, MD, PhD, of the Technion-Israel Institute of Technology. Tumors that are fueled by estrogen have a better prognosis.