Denosumab Keeps Bones Strong during Prostate Cancer Treatment
Adapted from the NCI Cancer Bulletin.
Treatment with the monoclonal antibody denosumab increased bone mineral density (BMD) and reduced the risk of fractures in men who received a common treatment for prostate cancer that had not spread to other parts of the body, according to the results of a large, placebo-controlled clinical trial. The findings appeared in the August 20 New England Journal of Medicine.
The Hormone Ablation Bone Loss (HALT) trial included nearly 1,500 men with nonmetastatic prostate cancer who were undergoing androgen deprivation therapy, a treatment that can increase the risk of bone fractures. The trial showed that two injections of denosumab, one every 6 months, increased BMD in the lumbar spine (the lower back) by 5.6 percent, whereas men who were randomized to receive a placebo experienced a 1 percent decrease in BMD in the same region. Denosumab also increased bone density in other areas, including the neck and hip.
"The beneficial effects in the denosumab group appeared robust, as they were found as early as 1 month after therapy was begun and were sustained for 3 years," wrote lead investigator Matthew R. Smith, M.D., Ph.D., of Massachusetts General Hospital and his colleagues. The rates of adverse events were similar between the two treatment groups.
Denosumab is the first drug developed that targets a molecule called RANKL, which spurs the activity of cells called osteoclasts that break down bone. It works in a different way than several other classes of drugs, including bisphosphonates, that are currently used to treat osteoporosis and bone loss.
Publication of the trial results coincided with a meeting of an FDA advisory committee to consider whether denosumab should be approved by the agency for several indications. The committee voted in favor of an approval for denosumab for the treatment of bone loss in men receiving androgen deprivation therapy for nonmetastatic prostate cancer but against its use for bone loss prevention, due to the potential for the small, increased risk of certain infections, including skin and urinary tract infections, seen in some clinical trials involving denosumab.
"Some patients undergoing androgen deprivation therapy may not develop enough loss of BMD to cause an increased risk of bone fracture," explained James L. Gulley, M.D., Ph.D., of the Laboratory of Tumor Immunology and Biology in NCI's Center for Cancer Research, who was a voting member on the FDA advisory committee. "And the general feeling of the committee was, until we get more safety data, let's not recommend an indication for prevention of BMD loss," he said.