18F-FDG PET/CT Demonstrates Significant Response in Anaplastic Thyroid Carcinoma Treated With Combined Immunotherapy and Targeted Therapy.

Anaplastic thyroid carcinoma (ATC) is a rare but highly aggressive malignancy with a dismal prognosis and limited responsiveness to conventional therapies. Recent advances in targeted therapy and immunotherapy have shown promise in improving outcomes. 18F-FDG PET/CT serves as a valuable tool for evaluating disease extent and monitoring therapeutic response in ATC. We present the case of a 51-year-old woman diagnosed with biopsy-proven anaplastic thyroid carcinoma, presenting with extensive locoregional disease and pulmonary metastases on Pembrolizumab and Lenvatinib. 18F-FDG PET/CT was done for response assessment which showed near complete metabolic response.