Drug May Reduce Cancer Spread to Bone

Prostate cancer that has metastasized to the bone may be slowed by cabozantinib

(RxWiki News) Patients with advanced prostate cancer may have cancer cells that spread to the bone and cause pain. A new drug shows promise by rapidly reducing prostate cancer bone tumors.

Cabozantinib (Cometriq) recently won approval from the US Food and Drug Administration for the treatment of thyroid cancer. Studies have shown it may be effective in fighting liver, ovarian and other cancers as well.

Now new research has found cabozantinib may block the growth of prostate cancer that has spread to the bone and decrease the resulting pain.

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David C. Smith, MD, professor of internal medicine and urology at the University of Michigan Medical School in Ann Arbor, and his colleagues observed the effects of cabozantinib on a group of men whose cancer had metastasized (spread) to the bone.

Researchers followed the progress of 171 men with castration-resistant prostate cancer (CRPC) who received cabozantinib for 12 weeks. The phrase “castration-resistant” may be misinterpreted. It does not mean that the men are physically castrated. It is a term used to describe tumors that no longer respond to hormone-based therapy. Some hormone-based therapy drugs are euprolide (Lupron, Viadur, Eligard), goserelin (Zoladex), triptorelin (Trelstar) and histrelin (Vantas).

About two-thirds of these CRPC patients saw improvement on their bone scans. A bone scan is an imaging test that helps track cancer in the bone. Investigators noted complete resolution of uptake in 12 percent of the men, indicating that the drug was successfully making it to the targeted cancer cells.

About 7 out of 10 patients showed a reduction in soft tissue lesions.

At week 12, 31 patients with stable disease were randomly assigned to either receive cabozantinib or placebo. Of the 14 receiving the drug, cancer progressed after a median 24 weeks for patients taking cabozantinib, compared with 6 weeks for the 17 patients on placebo.

Randomization was stopped early because patients receiving placebo saw their cancer progress much more quickly than those that remained on drug.

In addition to the improvements on bone scans, 67 percent of patients with bone pain reported an improvement in pain control and 56 percent decreased or eliminated narcotic painkillers after treatment with cabozantinib.

“While these initial results are promising, we are still uncertain how cabozantinib will impact the gold standard of survival,” said Dr. Smith.

Dr. Smith told the dailyRx News, “Next steps are trials to define the mechanism of action of cabozantinib. Patients who want to explore treatment with cabozantinib should go on ClinicalTrials.gov and find the nearest center participating in the trials.”

When used for the treatment of medullary thyroid cancer, cabozantinib costs $9,900 for a 28 day treatment course. If dosages are the same, treatment cost would likely be similar for prostate cancer.

The study was published online in the November issue of the Journal of Clinical Oncology. Funding for research was provided by Exelixis, the manufacturer of cabozantinib.

Review Date: 
December 10, 2012