Side effects were commonplace but typically mild. The most usual were diarrhea, hypertension, and an increase in a liver enzyme called aminotransferase. However, 15 patients had to have their dose lowered because of side effects, the researchers note.
The U.S. National Cancer Institute funded the study.
Molina noted that larger phase 3 trials will start soon, and he hopes the drug, made by GlaxoSmithKline, will be approved for treating advanced thyroid cancer.
"One of the goals in cancer care is to make cancer a chronic disease," Molina said. "If we can make cancer something like that, where your pills keep your disease controlled, that's a good goal," he said.
One expert said that any effective therapy would be welcome.
"There are not a lot of treatment options available for people with advanced thyroid cancer," said Dr. Leonard Lichtenfeld, deputy chief medical officer at the American Cancer Society.
While the study results will need to be replicated and tested against other treatment options before pazopanib can be approved as a therapy for thyroid cancer, he agreed that the drug shows promise.
"Targeted therapies are providing some effective treatment options for patients with diseases that traditionally have been difficult to treat," he said. "I find that very helpful and very exciting."
For more information on thyroid cancer, visit the American Cancer Society.
SOURCES: Julian Molina, M.D., Ph.D., assistant professor of oncology, Mayo Clinic, Rochester, Minn.; Leonard Lichtenfeld, M.D., M.A.C.P., deputy chief medical officer, American Cancer Society, Atlanta; Sept. 17, 2010, The Lancet Oncology, online
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