Hormone therapy for advanced prostate cancer can lead to bone loss and fractures

A common type of treatment used to protect bone density in menopausal women is also an effective therapy for advanced prostate cancer patients during the first year of hormone therapy, according to a new Oregon Health & Science University Cancer Institute study.

"This is important because men treated for advanced prostate cancer are at great risk for losing bone density, which makes the bones vulnerable to fracture," said Christopher Ryan, M.D., a researcher with the OHSU Cancer Institute and lead author of the study. "Hip fractures are especially dangerous and can be life-threatening in older patients."

Hormone therapy, also known as androgen deprivation therapy, is the gold standard of care for men whose prostate cancer is advanced and has spread throughout the body. The therapy works by shutting down male hormones, principally testosterone, that can promote prostate cancer growth. This common treatment for prostate cancer wipes out most male hormones found in the body.

Loss of bone density is a serious side effect of hormone therapy for advanced prostate cancer, a finding that has come to light in recent years. Very low bone density results in a disease called osteoporosis, which is most recognized as a problem in women after menopause. These women are frequently treated with medicines called bisphosphonates that help renew bone growth by inhibiting cells responsible for bone loss.

Ryan studied 120 men with prostate cancer who had been on hormone therapy for up to a year. They found that administration of a bisphosphonate called zoledronic acid every three months significantly increased bone density during the course of 12 months. Men who received a placebo lost bone density.

Zoledronic acid previously has been shown to prevent bone mineral density loss in prostate cancer patients just beginning hormone therapy. "What's new about our study is that it shows starting zoledronic later is still effective and can recover bone density that already has been lost," Ryan said.

Researchers also found a positive effect of zoledronic acid on bone markers, measurements of bone loss that are found in blood and urine. This study supports current guidelines that recommend monitoring bone density of men on hormone therapy and initiating bisphosphonate treatment if the bone density falls.

Prostate cancer is the most common cancer in men and the second leading cause of cancer-related death in American men. Overall, 1 in 6 men will develop prostate cancer during his lifetime.