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Among men with bone metastases from prostate cancer, denosumab was more effective than Zometa® (zoledronic acid) at delaying or preventing bone complications such as fracture. Results from this Phase III clinical trial will be presented at the 2010 annual meeting of the American Society of Clinical Oncology.

Metastatic cancer refers to cancer that has spread to distant sites in the body. Several types of cancer—including prostate cancer—have a tendency to spread to the bone. Bone metastases can lead to serious problems such as fracture and spinal cord compression, and may require treatment with surgery or radiation therapy.

Bisphosphonate drugs such as Zometa are commonly used to reduce the risk of complications from bone metastases. Researchers continue, however, to explore new approaches to treatment.

Denosumab is a drug that targets a protein known as the RANK ligand. This protein regulates the activity of osteoclasts (cells that break down bone). Denosumab was recently approved for the treatment of postmenopausal osteoporosis, and has also shown promising results in the management of bone metastases and treatment-related bone loss.

To directly compare denosumab to Zometa among prostate cancer patients with bone metastases, researchers conducted a Phase III clinical trial. The study enrolled 1,901 patients with metastatic, hormone-refractory prostate cancer. Study participants were assigned to receive either denosumab or Zometa.

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The objective of the study was to determine whether the occurrence of bone complications (“skeletal related events”) differed between the two study groups. The bone complications that were evaluated were fracture, radiation to the bone, surgery to the bone, and spinal cord compression.

  • Patients treated with denosumab remained free of bone complications longer than patients treated with Zometa. Median time to first on-study bone complication was 20.7 months among patients treated with denosumab compared with 17.1 months among patients treated with Zometa. Denosumab also reduced the rate of multiple bone complications.
  • Overall survival and time to cancer progression were similar among patients treated with Zometa and patients treated with denosumab.
  • The most common side effects of denosumab were anemia, back pain, and nausea. The most common side effects of Zometa were anemia, back pain, and decreased appetite.
  • Osteonecrosis of the jaw (an uncommon but serious side effect) occurred in 2.3% of patients treated with denosumab and 1.3% of patients treated with Zometa. This difference between study groups was not statistically significant, suggesting that it could have occurred by chance alone.

The results of this study suggest that denosumab may be more effective than Zometa at delaying or preventing skeletal complications in prostate cancer patients with bone metastases.

Reference: Fizazi K, Carducci MA, Smith MR et al. A randomized phase III trial of denosumab versus zoledronic acid in patients with bone metastases from castration-resistant prostate cancer. Presented at the 2010 annual meeting of the American Society of Clinical Oncology. June 4-8, 2010. Chicago, IL. Abstract LBA 4507.

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