Common Prostate Cancer Treatment May Cause Severe Bone Loss, According To Researchers At The University Of Pittsburgh

“We were surprised to find that men who were treated with GnRH-a for prostate cancer experienced up to a decade's worth of bone loss within the first year of therapy,” said senior author Susan Greenspan, M.D., professor, divisions of endocrinology and geriatric medicine, department of medicine, University of Pittsburgh; and director, Osteoporosis Prevention and Treatment Center, UPMC.

GnRH-a works by depriving the body of testosterone, an androgen hormone that increases the growth of prostate tumors. However, testosterone also is essential to maintaining bone mass in men. While doctors have been using GnRH-a for more than a decade in treating men with late-stage metastatic prostate cancer, they have begun using it more recently in men with earlier-stage disease and for longer periods of time.

“In treating men with this therapy earlier and for longer periods of time, we are putting them in a menopause-equivalent condition and subjecting them to severe osteoporosis -- a disease that may have more serious consequences than early-stage prostate cancer,” said Dr. Greenspan. “With close to 200,000 men being diagnosed with prostate cancer each year, we could be facing an enormous increase in the incidence of debilitating bone fractures in men.”

In this study, investigators compared bone mineral densities (BMD), biochemical markers of bone turnover and body composition in 60 men with prostate cancer -- 19 of whom were on GnRH-a and 41 who were not -- and BMD in 197 healthy men.

While the prostate cancer patients who had not been treated with GnRH-a had BMDs that were similar to those of the healthy controls, the scores of men treated with GnRH-a showed dramatically different results in several categories.

The treated men had BMD levels that were up to 17 percent lower than those of untreated men, putting the treated men at a markedly higher risk for fracture. Treated men also had nearly double the levels of urinary NTx, a marker for bone resorption, indicating that their bones were disintegrating twice as quickly as the bones of untreated men. In addition, they had significantly lower blood counts and levels of estradiol, a hormone that is needed, along with testosterone, for bone health. Treated men also showed an increase in total body fat and loss of muscle mass.

“Clearly, cutting off testosterone production in men through the administration of GnRH-a has some very serious consequences related to skeletal integrity and overall health,” continued Dr. Greenspan. “This is particularly troubling because the greatest degree of bone loss appears to occur with the initiation of treatment.”

Dr. Greenspan is currently recruiting patients for a study to determine whether bisphosphonate, an anti-resorptive therapy, can prevent or abate bone loss in men who are being treated with GnRH-a for prostate cancer. For more information about participating in this study, please call the UPMC Osteoporosis Prevention and Treatment Center at 412-692-2220.