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From Spring 2014 Quest

Hormonal therapy is meant to target or block the production of male hormones, or androgens. Theoretically, hormonal therapy would stop the growth of prostate cancer cells that need androgen to reproduce.

However, prostate cancer cells can develop resistance to conventional hormonal therapy. This condition is called metastatic castration-resistant prostate cancer. New treatments are becoming available for this condition.

Radium-223 Trial a Success

Researchers reported favorable results from a phase 3 study analyzing radium-223 in men with castrationresistant prostate cancer with bone metastases. The study showed that radium-223 prolonged overall survival with a 30% reduction in the risk of death when compared to the placebo.

Radium-223 is a targeted alpha particle emitter that naturally travels to the bone. There, it releases high-energy alpha particles with a short range, which limits damage to other tissue.

The researchers said that at least 20-40% of patients with castration-resistant prostate cancer and bone metastases never receive chemotherapy, and current therapies that target the bone have not been proven to improve survival rates. Radium-223 could help this group of men who are not receiving other types of treatment.

Radium-223 was recently approved for use to treat prostate cancer with bone metastases in the US.

Parker C. et al. Alpha-Emitter Radium-223 and Survival in Metastatic Prostate Cancer. N Engl J Med. 2013; 369(3);213-223

Cabozantinib undergoing trials for prostate cancer

The drug cabozantinib is being studied for treatment of metastatic castration-resistant prostate cancer. A phase 2 study of cabozantinib with a dosage of 100 mg daily showed improvement in bone scans, but patients experiencing adverse events caused frequent dose reductions. A study published in Clinical Cancer Research examined the efficacy of the drug at lower doses. Patients who took cabozantinib at a dosage of 40 mg daily were associated with a high rate of bone scan response and reported better tolerability than patients who took the drug at a higher dose. These results informed the design of the phase 3 studies for cabozantinib, which are currently enrolling patients.

Lee R. et al. A dose-ranging study of cabozantinib in men with castration-resistant prostate cancer and bone metastases. Clin Cancer Res. 2013; 19(11):3088-94

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