Clinical Value of 18F-Fluorodeoxyglucose (FDG) Positron Emission Tomography (PET)/Computed Tomography (CT) in Radioiodine-Refractory Thyroid Carcinoma: A Case Report.

Radioiodine-refractory differentiated thyroid cancer is a condition that arises in patients who develop resistance to the mainstay treatment for thyroid cancer. Although it is relatively uncommon, its clinical significance lies in the fact that it markedly worsens prognosis and calls for the implementation of alternative management strategies for affected patients. This is a case of a 40-year-old woman with a 17-year history of differentiated thyroid cancer, refractory to radioiodine (RAI), showing no iodine-131 uptake on whole body scan scintigraphy and elevated tumor markers. Through 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) imaging, hypermetabolic foci were identified in the lungs, consistent with metastatic recurrent disease. Due to its effectiveness, 18F-FDG PET/CT should be considered for evaluation in cases of clinical suspicion in patients with elevated tumor markers and low iodine-131 uptake, consistent with radioiodine-refractory disease.