A combination of the drugs pazopanib and paclitaxel shows promise in slowing anaplastic thyroid cancer (ATC), according to a Mayo Clinic-led study published in the journal Science Translational Medicine. The two drugs together resulted in greater anti-cancer activity in ATC than either drug alone, says lead researcher Keith Bible, M.D., Ph.D., a Mayo Clinic oncologist.
Anaplastic thyroid cancer is a rare but devastating form of thyroid cancer that typically strikes men and women in their 60s and 70s. It is very aggressive, with a median survival of only about 5 months from time of diagnosis. Only 20 percent of patients survive a year beyond diagnosis, and it has historically been found to be resistant to most therapies.
Pazopanib, a kinase-inhibitor that interferes with the growth of cancer cells, is already approved by the Food and Drug Administration (FDA) to treat renal cancer tumors. Paclitaxel is an FDA-approved chemotherapy drug that disrupts the machinery involved in cell division.
Researchers studied anaplastic thyroid cancer cells and tumors in cell culture and in animal models. Human ATC cells were readily killed, and ATC tumors implanted into mice were 50 percent smaller when treated with the combination in comparison to the response to treatment with either drug alone. Pilot therapy of one patient with metastatic anaplastic thyroid cancer using the combination also resulted in marked tumor shrinkage lasting over six months. "This was a highly unexpected finding for this type of aggressive tumor, which often can double in size in a matter of days," Dr. Bible says.
In previous studies, pazopanib alone was found not effective in the treatment of anaplastic thyroid cancer. Paclitaxel was added to address the aggressiveness of anaplastic thyroid cancer tumors and bolster anti-cancer effects. The team investigated how the two drugs might complement each other.