Imaging Response to Ensartinib in Concurrent Papillary and Anaplastic Thyroid Carcinoma With ALK Rearrangement.

A 67-year-old woman with coexisting papillary thyroid carcinoma (PTC) and anaplastic thyroid carcinoma (ATC) harbored an ALK rearrangement on FISH. Despite surgery and 2 courses of 131 I treatments, 18 F-FDG PET/CT showed an intensely avid right lower-neck mass extending into the superior mediastinum. The patient was considered radioiodine-refractory (RAIR) and started ensartinib (225 mg once daily). CT at 3 months showed marked regression, with sustained disease control at 12 months. This case illustrates an objective imaging response to ALK-directed therapy in RAIR thyroid carcinoma.