This is an open label, non-randomized study to evaluate the efficacy and safety of the combination of larotrectinib followed by 131I therapy for patients with NTRK fusion differentiated thyroid cancer. The primary Phase II objective will be to evaluate the pulmonary structural response rate at 18 months to the combination of larotrectinib given for 6-months followed by 131I therapy.
Papillary thyroid cancer (PTC) is the most common form of differentiated thyroid cancer (DTC). The traditional first line treatment for patients with advanced DTC after surgical resection is radioactive iodine (RAI) therapy. However, less than a quarter of patients with lung metastases will achieve a complete response to RAI therapy, and this therapy carries the risk of pulmonary fibrosis and an increasingly recognized risk of secondary malignancies.