Men with prostate cancer taking drugs that suppress their testosterone production may develop weak bones as a result. Now, a drug called pamidronate has been found to prevent bone loss in these patients, according to a report in the Sept. 27th issue of the New England Journal of Medicine (Vol. 345, No. 13: 948-954).

Prostate cancer is often stimulated to grow by a man’s testosterone. One of the standard treatments for advanced prostate cancer is to block testosterone production, (androgen-deprivation) either with drugs or as was done in the past, removing the man’s testicles.

But testosterone is responsible for the typical male characteristics, including strong bones, increased muscle strength, and male-pattern baldness. Because of their lowered testosterone levels, however, men undergoing this therapy can lose bone density and develop osteoporosis, which can lead to bone fractures.

Matthew R. Smith, MD, PhD, with Harvard University’s Massachusetts General Hospital in Boston, and his colleagues wanted to see if a drug called pamidronate could help prevent bone loss in men undergoing androgen deprivation therapy.

Pamidronate belongs to a class of drug called bisphosphonates, which are known to prevent bone loss in patients with other disorders linked to osteoporosis. Smith and his colleagues questioned whether pamidronate would work for these men as well.

The researchers studied 43 prostate cancer patients who were taking Lupron, a drug that suppresses testosterone. Twenty-one of the men were given pamidronate along with Lupron, while the other 22 received the Lupron but no pamidronate.

At 48 weeks, men who did not take pamidronate lost an average of 8.5% of their bone mineral density (a measure of bone strength) in the lumbar spine (lower back). They also lost bone mineral density to a lesser extent at several other sites.

In contrast, men taking pamidronate kept their normal bone density at all the sites.

“Pamidronate has been shown to work in other types of patients with osteoporosis, so it wasn’t surprising that it worked in these patients,” Smith says. “But the importance of the study is that it highlights the problem of osteoporosis in men.”

According to Smith, the problem of osteoporosis in men is under appreciated. “There’s a general misunderstanding that men don’t get osteoporosis — but that’s not true. One third of all hip fractures occur in men. But what’s also under appreciated is that androgen-deprivation therapy for prostate cancer results in high rates of bone loss,” he says.

Smith recommends that men should be screened for osteoporosis, whether or not they are taking androgen-deprivation therapy. “They should also exercise regularly and take a daily calcium supplement and a multivitamin containing vitamin D,” which can also reduce bone loss, he suggests.

“Bone loss due to this treatment is an increasingly relevant issue, because this type of treatment for prostate cancer is now routinely used early in the illness in men who are well and who have a long life expectancy,” Smith says. “So this side effect requires even more attention,” he emphasizes.

According to J. William Eley, MD, MPH, associate professor at the Rollins School of Public Health at Emory University in Atlanta, “these results are not surprising based on our knowledge of the effects of the bisphosphonates on bone loss in other groups.”

But Eley points out that larger studies are needed. “This is a small trial, which should be followed up by larger trials,” he says. “I think the standard of care should not change based solely on this study — this is just one person’s opinion.”

Eley also points out the study examined an indirect measure of fracture risk — bone density — which can only predict the fractures likely to take place in the future. But he says, “the results of this study are another example of one step toward a new therapy that may improve quality of life for cancer patients.”