Among prostate patients treated with androgen deprivation therapy, the investigational drug denosumab increases bone density and reduces the risk of fractures. Denosumab also improves bone density in breast cancer patients treated with aromatase inhibitors. These were the results of two studies presented at the 2009 annual meeting the American Society of Clinical Oncology (ASCO).
Hormonal therapy plays an important role in the treatment of many patients with breast or prostate cancer. In men with prostate cancer, androgen deprivation therapy (ADT) reduces circulating testosterone. And in women with hormone receptor-positive breast cancer, treatment with tamoxifen (Nolvadex®) or aromatase inhibitors reduces exposure to estrogen.
Although these therapies have made notable contributions to improved cancer outcomes, ADT and aromatase inhibitors (but not tamoxifen) have also been linked with bone loss. Bone loss can lead to osteoporosis and fractures.
Denosumab is an investigational drug that targets a protein known as the RANK ligand. This protein regulates the activity of osteoclasts (cells that break down bone). Denosumab is being evaluated for the management of bone loss among patients with a variety of conditions, including cancer patients with treatment-related bone loss.
In one of the studies presented at ASCO, researchers evaluated the effects of denosumab on fracture risk among more than 1,400 men receiving ADT for nonmetastatic prostate cancer. Half the men were given denosumab every six months for three years and half were given a placebo. The results showed that men in the denosumab group were 62% less likely than men in the placebo group to develop a new vertebral fracture. There was also some evidence that denosumab may decrease the risk of nonvertebral fractures.
Another study evaluated the effects of denosumab on bone density. Study participants were postmenopausal women with low bone density who were receiving aromatase inhibitor therapy for nonmetastatic breast cancer or men receiving ADT for nonmetastatic prostate cancer. In both groups of patients, treatment with denosumab resulted in significantly higher bone density at the lumbar spine, hip, and wrist than treatment with placebo.
These studies provide additional evidence that treatment with denosumab provides bone benefits to breast and prostate cancer patients who are at risk of bone loss as a result of cancer treatment.
 Saad F, Smith MR, Egerdie B et al. Denosumab for prevention of fractures in men receiving androgen-deprivation therapy (ADT) for prostate cancer. Presented at the 2009 annual meeting of the American Society of Clinical Oncology, May 29-June 2, 2009, Orlando, FL. Abstract 5056.
 Smith MR, Ellis G, Saad F et al. Effect of denosumab on bone mineral density (BMD) in women with breast cancer (BC) and men with prostate cancer (PC) undergoing hormone ablation therapy. Presented at the 2009 annual meeting of the American Society of Clinical Oncology, May 29-June 2, 2009, Orlando, FL. Abstract 9520.