SUVmax of 18F-FDG PET/CT in the differential diagnosis of benign and malignant thyroid nodules according to tumor volume.

Background: The aim of this study was to investigate whether the maximum standardized uptake value (SUVmax) measured on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) could be used as the primary means of differential diagnosis of thyroid nodules when tumor volume is assessed.

Methods: We studied 192 patients who underwent preoperative 18F-FDG PET/CT followed by thyroidectomy. We evaluated the correlation between the volume of thyroid nodules, 18F-FDG uptake on visual analysis, and the mean SUVmax measured on 18F-FDG PET/CT.

Results: When stratified by tumor volume, the mean SUVmax was higher in malignant than in benign nodules in nodules≥1 cm3 (p<0.001). However, it did not differ between benign and malignant nodules smaller than 1 cm3. At a cut-off value of SUVmax of 6, the respective sensitivities of 18F-FDG PET/CT, ultrasonography, and fine needle aspiration cytology were 60.8, 96.4, and 99.1%, and the respective specificities were 95.9, 98.2, and 96.8%.

Conclusions: 18F-FDG PET/CT is limited as a primary modality in the differential diagnosis of benign and malignant thyroid nodules because of its low sensitivity.