Hormone-suppressing drugs increasingly used to treat prostate cancer make men so prone to broken bones that the risks of the treatment may outweigh the benefits in those whose cancer was caught early, researchers say.

Researchers at the University of Texas medical branch at Galveston found that in the five years after prostate cancer was diagnosed, men taking such drugs had a 20 per cent risk of fracture, versus 13 per cent among those not getting the treatment.

While prostate cancer kills about 30,000 American men a year, it generally grows slowly, and most patients die of some other cause before the cancer can kill them.

At the same time, a broken bone can prove lethal. For elderly people, a serious fracture often starts a downward spiral of slow-healing infections and other complications, confinement to a nursing home or hospital bed, and eventually death. One-third of elderly men who break their hips die of complications within a year.

"If there's no survival benefit and there's potential harm, you should consider whether you should put these men on hormonal deprivation therapy," said Dr. Ronald Morton, director of urologic oncology at the Cancer Institute of New Jersey.

The study, led by Dr. Vakahn Shahinian, an assistant professor of internal medicine, reviewed health records of 50,613 men with prostate cancer, age 66 or older, from national databases on cancer and Medicare patients. It was reported in Thursday's New England Journal of Medicine.

The researchers blamed hormone-suppressing drugs for an estimated 3,000 fractures a year in Americans with prostate cancer, the second-most common and second-most deadly cancer among men.

About 40 per cent of the 230,000 men diagnosed with prostate cancer in this country each year get drugs such as Lupron to suppress production of male hormones like testosterone. That is because testosterone, which helps build up bone and muscle, also can induce growth of prostate cancer cells. Those drugs, when combined with radiation, have been proven to save lives among men with advanced prostate cancer.

But in recent years, doctors have also been giving hormone-suppressing drugs to men where there is no clear proof the additional treatment helps, such as early cases where the cancer has not spread beyond the prostate gland.

"What doctors should be telling their patients is, 'We don't know that we'll be lengthening your life, but we do you know that we may be increasing your risk of fracture,' " said Dr. Durado Brooks, director of prostate cancer for the American Cancer Society.

Morton and other experts said doctors should also consider giving drugs such as Fosamax that can slow and sometimes reverse bone loss.

The study found that among men surviving five years after their cancer diagnosis, for those getting hormone suppression, the risk of a fracture requiring hospitalization doubled, as did the risk of a spine, hip or upper leg fracture, compared with the group who did not get the treatment.

Morton said doctors generally tell men about the hormone-suppression therapy's other side-effects: loss of muscle mass and strength, loss of some mental sharpness, and hot flashes. But few have brought up the fracture risk until recently, he said.

Morton said one weakness of the study is that for unexplained reasons the group getting the hormone-suppression therapy had more fractures before their cancer was diagnosed than the other group. Morton said a study that follows patients longer, and periodically collects data on bone density, would be more definitive.