MONDAY, Sept. 18 (HealthDay News) -- Hormone therapy for men with prostate cancer has become a mainstay of treatment, but a new Harvard study finds that the treatment increases the risk for diabetes and heart disease without improving survival.

Hormone therapy for prostate cancer involves blocking testosterone production. This can be done by removing the testes, called a bilateral orchiectomy, or more commonly through injections of a gonadotropin-releasing hormone (GnRH) agonist drug.

Dr. Nancy Keating, an assistant professor of health care policy and medicine at Harvard Medical School, said, "There is evidence that GnRH therapy helps with some pain and may slow the progression of metastatic disease. It is clearly indicated for some men, with advanced tumors."

But, Keating added, there's no conclusive evidence that in men with localized prostate cancer the therapy prolongs life. Many men receive hormone therapy not because of proven results, but because doctors and patients want to feel they are doing something to fight the disease, she said.

The study findings are published in the Sept. 20 issue of the Journal of Clinical Oncology.

Testosterone-suppressing drugs aren't benign, Keating said. "There is evidence that these drugs decrease quality of life, that they decrease bone mass and are associated with an increased risk of fractures. Men also develop central obesity and lose muscle mass and develop insulin resistance, which is a precursor for diabetes," she said.

Based on these findings, Keating's group sought to find out if men receiving hormone therapy actually were at risk for developing diabetes and heart disease.

In its study, Keating's team collected data on 73,196 men, 66 and older, diagnosed with prostate cancer from 1992 to 1999. The researchers followed the men through 2001. Among these men, one-third were given GnRH therapy.

The researchers found that men receiving a GnRH agonist had a 44 percent increased risk of diabetes, a 16 percent increased risk of coronary heart disease, an 11 percent greater risk of a heart attack, and a 16 percent increased risk of sudden cardiac death.

Men who had an orchiectomy had a 34 percent increased risk of developing diabetes, but did not face heightened risk of coronary heart disease, heart attack, or sudden cardiac death, Keating's group found.

"There is clear evidence that over the last decade these drugs are being used way more frequently than they ever were before," Keating said. "There is some question whether there is overuse of these drugs," she added.

Patients and doctors should be careful before undertaking hormone therapy, Keating said.

"We want to encourage doctors and their patients to be cautious before jumping on a potentially toxic medication," she said. "Men with locally regional prostate cancer have almost 100 percent five-year survival rates. Most of these men won't die of their prostate cancer. We certainly don't want to be giving them heart attacks and diabetes."

One expert thinks that, given these findings, men should carefully weigh the consequences of hormone therapy before starting it.

"This study raises an important question," said Dr. Herman Kattlove, a medical editor at the American Cancer Society. "It raises the question whether there really is a difference between treating patients with drugs to reduce their testosterone or performing an orchiectomy."

Kattlove noted that the study does not really answer that question. Only a prospective, randomized trial would do that, he said. But given these new findings, men should be cautious about hormone therapy, he said.

"Men should take a second look," Kattlove said. "They should think about their decision and the increased risk if they do take the drug, since there really is no difference in final outcome whether you have one of these drugs or have an orchiectomy."

More information

The American Cancer Society has more on prostate cancer.