Clinical trial shave shown that a kinase inhibitor called cabozantinib could possibly be used as a first line treatment against differentiated thyroid cancer.
Scientists have said that this option could be viable for patients with metastatic, radioactive iodine-resistant thyroid cancer. In a trial initiated and led by the Abramson Cancer Center and the Perelman School of Medicine at the University of Pennsylvania, tumors shrunk in 34 out of 35 patients who took the drug, and more than half of those patients saw the tumor size decrease by more than 30 percent.
Currently patients with differentiated thyroid cancer are given radioactive iodine therapy. Since the thyroid absorbs nearly all of the iodine in the human body, radioactive iodine given to a patient will concentrate in thyroid cancer cells, killing them with little effect on the rest of the body. The treatment can be curative, but about 15 percent of these patients have cancers that are resistant to the therapy. There are currently two approved treatments in these cases, both of which are kinase inhibitors – drugs that block enzymes that are crucial to a cancer cell’s ability to function. However, responses to these treatments are not durable. Once patients progress, they need additional therapeutic options.
As part of a phase II trial, researchers gave the drug as a first line therapy to 35 patients with metastatic, radioactive iodine-resistant thyroid cancer starting in March of 2014. Thirty-four experienced tumor shrinkage, and 19 of the 35 (54 percent) achieved a partial response – defined as a shrinkage greater than 30 percent. The median time on the study was 35 weeks (range 3-197), and 16 patients are currently still enrolled.
“These results indicate cabozantinib may offer an additional treatment option to these patients that will shrink tumors and provide an additional progression-free period for our patients,” one of the scientists said.
Twenty-three of the 35 patients (66 percent) required dose interruptions and dose adjustments during the trial. The most common toxicities attributable to cabozantinib included hyperglycemia, which presented in 28 patients (80 percent). Twenty-seven patients experienced diarrhea (77 percent), 26 had fatigue (74 percent), and 25 had weight loss (71 percent). Five patients experienced grade 3-5 hypertension (14 percent), 3 had grade 3-5 increase lipase (9 percent), 2 had grade 3-5 weight loss (6 percent), 2 had grade 3-5 pulmonary embolism (6 percent), and 2 had hyponatremia (6 percent).