Clinical utility of vandetanib in the treatment of patients with advanced medullary thyroid cancer

Vandetanib (ZD6474) became the first systemic agent to be approved for the treatment of metastatic or locally advanced medullary thyroid cancer. It was a proof of principle, because it is an orally bioavailable medication that targets the growth factors felt to be important in the pathogenesis of this disease, ie, the rearranged during transfection proto-oncogene and vascular endothelial growth factor receptor. It was tested initially in two Phase II studies at doses of 100 mg and 300 mg daily. Although activity was seen at both doses, the higher dose was chosen for a randomized, placebo-controlled Phase II study. This trial, which accrued more than 300 patients, showed a statistically significant benefit for the group taking vandetanib compared with those taking placebo medication. Progression-free survival for the vandetanib arm has not been reached, compared with 19 months for the placebo arm. The main toxicity appears to be diarrhea, although some patients experienced significant side effects, including torsades de pointes and sudden cardiac death. Therefore, it is now necessary for practitioners to enroll in a Risk Evaluation Mitigation Strategy before being allowed to prescribe this medication, to reduce the risk of serious side effects occurring.