US Pharm. 2010;35(10):HS-32.According to Mayo Clinic researchers, pazopanib may be effective against metastatic, rapidly progressive differentiated thyroid cancers. Scientists studied 37 patients with the aggressive form of thyroid cancer and found that 18 patients showed a long-lasting response to pazopanib. Among these patients, 12 are still alive without disease progression, and the median progression-free survival time was 11.7 months, with an overall survival rate of 81% at 1 year. The findings of the phase II clinical trial, which were published in The Lancet Oncology, are the highest response rate reported to date in aggressive cases of differentiated thyroid cancer to their knowledge, the researchers said. They cautioned, however, that this drug is not intended for treating slow-growing differentiated thyroid cancers and that they cannot assess the survival advantage pazopanib offers to the patients studied. This would require a randomized clinical trial.
“In this group of patients, we would have expected the cancer to have progressed in everyone within 6 months, but instead the median time to progression was almost a year in response to pazopanib therapy,” said Keith Bible, MD, PhD, a medical oncologist and researcher who led the National Cancer Institute-funded, multicenter clinical trial. Despite the encouraging response, pazopanib does not come without the potential for significant side effects, Dr. Bible said. Given this potential, therefore, patients with slow-growing thyroid cancer should not use pazopanib.