New drug for bone loss

ADT, a common treatment for men with advanced prostate cancer, has been shown to speed up bone loss and increase the risk of fractures. This study investigated the effects of a new drug, denosumab, on bone mineral density (BMD) and fractures in men receiving ADT. Denosumab is a human monoclonal antibody that targets a protein (RANKL) that promotes bone breakdown.

In this phase III study, men with nonmetastatic prostate cancer who were on ADT were randomly put into two different groups: One group of 734 men were given a subcutaneous injection of denosumab, and another 734 a placebo, every six months for three years. All the men took daily supplements of calcium and vitamin D. The main objective of the study was to measure the change in BMD at the lumbar spine from baseline to month 24. Other endpoints included new fractures at the spine or any other sites over 36 months.

At 24 months, spinal BMD increased by 6.7% in the group taking denosumab compared with the men who received a placebo. BMD at the hip and femoral neck also increased significantly in the denosumab group. Denosumab was associated with a 62% reduction in vertebral fractures after 36 months, and a smaller (but not significant) decrease in fractures at other sites. Side effects were similar for men in both study groups.

The authors concluded that denosumab given twice yearly increased BMD at all measured skeletal sites and reduced the incidence of vertebral fractures significantly over three years in men with nonmetastatic prostate cancer receiving ADT.