Cohort study exploring the effect of lenvatinib on differentiated thyroid cancer.

Lenvatinib is a molecular-targeting agent that was recently approved in Japan for treatment of curatively unresectable, radioactive iodine-refractory, progressive differentiated thyroid cancer (DTC). Because only a few Japanese patients have received lenvatinib in clinical trials, there are limited domestic data on its safety and efficacy or prognostic factors. Therefore, a prospective observational study has been designed to collect safety and efficacy data in at least 300 patients with curatively unresectable DTC receiving lenvatinib therapy (24 mg/day), in order to find predictors of antitumor activity and survival. Patients with progressive curatively unresectable DTC refractory to radioiodine therapy will be enrolled and the primary endpoint will be overall survival. This study is designed to estimate the 95% confidence intervals of the 1-year and 2-year survival rates with a two-sided width of less than 10%. Secondary endpoints will be the time to treatment failure, time to strategy failure, progression-free survival time with clinical progressive disease, response rate, quality of life, safety, and patient reports. The ultimate goal is to obtain information for developing evidence-based guidelines for treatment of DTC, including recommendations on patient selection, dosages, and duration of treatment. This study has been registered with the UMIN Clinical Trials Registry (UMIN000022243).