Long-term Treatment of Pediatric Metastatic Papillary Thyroid Cancer With Lenvatinib.

Papillary thyroid carcinoma (PTC) is the most common pediatric thyroid malignancy and incidence is increasing. Standard treatment for PTC in pediatric patients includes surgical intervention, suppression of TSH with levothyroxine, and radioactive iodine therapy (RAI) in select patients. In the setting of metastatic PTC or PTC refractory to RAI therapy, tyrosine kinase inhibitors (TKIs), such as lenvatinib, may be used. Until recently, experience with these targeted agents were largely limited to adult patients with progressive or refractory PTC. More recently, increased experience with TKI therapy has been reported in the pediatric population, with case reports and small series describing short-term TKI use. We report the case of a 15-year-old girl with RAI-refractory metastatic PTC who achieved stable disease with long-term lenvatinib treatment for more than 5.5 years. Prospective, longitudinal studies of TKIs in RAI-refractory pediatric PTC are needed.