Positive phase 1 results in solid tumors prompted a phase 2 trial in patients with advanced, radioiodine-refractory, differentiated thyroid cancer (RR-DTC).METHODS: Fifty-eight patients with RR-DTC who had disease progression during the previous 12 months received lenvatinib 24 mg once daily in 28-day cycles until disease progression, unmanageable toxicity, withdrawal, or death.