According to the results of a Phase II clinical trial among women with breast cancer-related bone metastases, the experimental drug denosumab appears to reduce bone turnover and the risk of problems such as fractures to a similar extent as bisphosphonate treatment. These results were published in the Journal of Clinical Oncology.
The spread of cancer from its site of origin to another location in the body is called metastasis. Bone is one of the most common locations in the body to which cancer metastasizes. The major cancer types that tend to metastasize to bone include multiple myeloma, breast, prostate, lung, kidney, and thyroid cancers.
Cancer cells that have spread to the bone disrupt the balance between the activity of osteoclasts (cells that break down bone) and osteoblasts (cells that build bone). Bone metastases may cause pain, may make the bones more susceptible to fractures, and may cause increased levels of calcium in the blood.
Bisphosphonates are a class of drugs used for the treatment of cancer-related hypercalcemia (high levels of calcium in the blood) and of bone metastases in patients with advanced cancers. Bisphosphonates decrease the rate of bone destruction in patients with bone metastases. As well, clinical studies have demonstrated that bisphosphonates can significantly decrease the pain and number of fractures occurring from bone metastases.
While bisphosphonates provide important benefits to many patients with bone metastases, not all patients respond to treatment, and some patients experience adverse effects. Researchers have therefore continued to explore other approaches to the management of bone metastases.
Denosumab is an experimental drug that is intended to suppress bone resorption. To evaluate the effects of denosumab in women with breast cancer-related bone metastases, researchers conducted a Phase II clinical trial. The trial enrolled 255 women from North America, Australia, and Europe. None of the women had previously received bisphosphonate therapy.
Study participants were assigned to one of five different dosing schedules of subcutaneous denosumab, or to treatment with an intravenous bisphosphonate.
- By 13 weeks the percent of patients who achieved a specified reduction in bone turnover was 74% among patients treated with denosumab and 63% among patients treated with a bisphosphonate.
- Skeletal-related events (fracture, surgery or radiation to bone, or spinal cord compression) occurred among 9% of women treated with denosumab and 16% of women treated with a bisphosphonate.
- There were no serious adverse effects of treatment among patients treated with denosumab.
The researchers conclude that the ability of denosumab to suppress bone turnover and to reduce the risk of skeletal-related events such as fractures may be similar to that of bisphosphonates. Phase III clinical trials of denosumab are underway and will provide additional information.
Reference: Lipton A, Steger GG, Figueroa J et al. Randomized active-controlled phase II study of denosumab efficacy and safety in patients with breast cancer-related bone metastases. Journal of Clinical Oncology. 2007;25:4431-4437.
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