A commonly used prostate cancer treatment (search) increases the risk of a bone fracture, research shows.

Prostate cancer cells grow in response to testosterone (search). Using hormone therapy to block the effect of testosterone has become an increasingly common prostate cancer treatment in the last 15 years, say researchers in The New England Journal of Medicine.

Hormone therapy (search) is used to reduce tumor growth. It can improve a patient's chance of surviving prostate cancer. In recent years, it’s been used to treat prostate cancer that hasn’t spread beyond the prostate and to curb high levels of prostate-specific antigen (PSA) after prostate removal.

But hormone therapy also weakens the bones, making them easier to break. Suppressing male hormones raises the risk of osteoporosis, a condition much more commonly associated with postmenopausal women.

In this new study of more than 50,000 prostate cancer patients, almost a fifth of the men on hormone therapy suffered a bone fracture in the five years following their diagnosis. In comparison, just under 13 percent of men not on hormone therapy had bone fractures during that time.

Fracture risk was linked to hormone therapy dose. Taking nine or more doses in the year after diagnosis made men 1.5 times more likely to fracture their hip, spine, or forearm. A similar risk was seen in men who had their testicles removed, another way to thwart production of male hormones.

Hormone therapy medications for prostate cancer include:

Lupron (search) and Zoladex (search). These are man-made hormones that block the production of testosterone in the testicles. These medications are given as shots.

An implant, called Viadur (search), also is available. Implants most often are used to help control symptoms of advanced prostate cancer, such as pain and difficulty urinating.

Casodex, Eulixin and Nilandron. About 10 percent of testosterone is produced by the adrenal glands (search). In men whose testicles have been removed or are not making testosterone (such as those taking Lupron and Zoladex), adrenal testosterone can become a concern. Casodex (search), Eulixin (search), and Nilandron (search) are medications that block the action of any remaining testosterone either by suppressing its production by the adrenal glands or by stopping testosterone from "attaching" to prostate cancer cells. They are given as pills.

What Should Men Do?

The increased risk is moderate but important, say the researchers, who included Vahakn Shahinian, MD, of the University of Texas Medical Branch. They estimate that hormone therapy drugs could prompt about 3,000 fractures per year.

Men on hormone therapy for prostate cancer should talk to their doctors about a way to decrease their chance of having a fracture. There are tests that can be used to help determine a man’s risk of a fracture. And medications can also help prevent bone weakening if necessary.

By Miranda Hitti, reviewed by Michael W. Smith, MD

SOURCES: Shahinian, V. The New England Journal of Medicine, Jan. 13, 2005; vol 352: pp 154-164. WebMD Medical News: “Prostate Cancer Drugs Raise Osteoporosis Risk.” WebMD Medical Reference provided in collaboration with The Cleveland Clinic: "Hormone Treatment for Prostate Cancer."