An osteoporosis drug can protect against the bone damaging side effects of certain breast cancer medications, according to scientists.

The study indicates that some breast cancer patients could take zoledronic acid in addition to anti-cancer medications to maintain bone health.

Breast cancer drugs known as aromatase inhibitors stop the production of estrogen in postmenopausal women and therefore make less estrogen available to stimulate the growth of certain breast cancer cells.

Many postmenopausal women who have breast cancer are treated for several years with these life-saving drugs, but the inhibitors can also cause bone loss and fractures.

In a five year study, researchers from the University of Pittsburgh Cancer Institute found that women with early breast cancer who supplemented their anti-cancer drugs with zoledronic acid could prevent bone loss and actually show increases bone density over time.

Zoledronic acid was more effective when taken in advance, rather than waiting for fractures or other bone problems to occur.

"This study shows that bone loss from aromatase inhibitors can be prevented long term with a safe and effective drug that prevents osteoporosis," said Dr. Adam Brufsky of the University of Pittsburgh Cancer Institute.

Zoledronic acid is currently approved by the U.S. Food and Drug Administration for conditions including osteoporosis and bone complications of cancer.

The study was published in the journal Cancer.