FRIDAY, Sept. 17 (HealthDay News) -- A targeted drug called
pazopanib could prove effective against difficult-to-treat cases of
thyroid cancer cases, researchers say.
Most thyroid cancers can be treated with surgery or radioiodine,
but about 5 percent of patients will develop an aggressive,
life-threatening form of the disease.
Pazopanib (Votrient), already approved by the U.S. Food and Drug
Administration for treating advanced kidney cancer, works by
inhibiting growth of blood vessels essential for tumor growth and
"Thyroid cancers, when they grow, they need to form a lot of blood vessels," explained researcher Dr. Julian Molina, an assistant professor of oncology at the Mayo Clinic and co-author of the study. "For blood vessels to grow, the growth factor VEGF is required, and the drug targets this protein," he said.
Not only does the drug block production of new blood vessels, it
also interferes with the tumor cells' ability to continue growing,
Pazopanib, a pill that's taken daily, doesn't have the severe
side effects of standard chemotherapy, Molina said. But it is
expensive. According to the U.S. Department of Health and Human
Services, the average wholesale price, which is used to set drug
reimbursements, is $6,595 a month.
For this phase 2 study, published in the Sept. 17 online edition
The Lancet Oncology, Molina and colleagues tested the efficacy and safety of pazopanib in 37 patients with advanced, rapidly progressing thyroid cancer.
About half of the patients --18 -- had a partial response to the
drug, meaning their tumor shrank 30 percent or more, Molina said.
None had a complete response, in which the tumor disappears
completely, he added.
Twelve patients are still responding to the drug about a year
later. "Patients take the drug until the drug is no longer
effective," Molina said, noting these patients still take pazopanib
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
"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.