Usefulness of PET/CT in the diagnosis of recurrent or metastasized differentiated thyroid carcinoma

Abstract

The aim of the present study was to determine the usefulness of the positron emission tomography/computed tomography (PET/CT) with 18F-fluorodeoxyglucose (FDG) in the detection of recurrence or metastasization of differentiated thyroid carcinoma (DTC) in patients with abnormal thyroglobulin levels and negative findings on the 131I-diagnostic whole-body scanning (dWBS). Fifteen patients with DTC, abnormal thyroglobulin levels, and negative 131I‑dWBS findings were scanned using the 18F‑FDG PET/CT. Positive diagnosis was based on postoperative histologic findings, and clinical and imaging follow‑up results obtained in the subsequent 6 months. In addition, preoperative and postoperative thyroglobulin levels were compared. Using the findings of 18F‑FDG PET/CT and data on confirmed positive diagnosis, sensitivity and positive predictive value (PPV) were calculated. Sensitivity and PPV of PET/CT in detecting recurrence or metastasisization of DTC were 93.30 and 91.40%, respectively. Furthermore, postoperative thyroglobulin levels were markedly lower compared to the preoperative levels (respectively, 4.67±1.71 vs. 58.53±18.34 ng/ml; p<0.05). PET/CT scan with 18F‑FDG is an informative technique for the detection of recurrent or metastasized DTC in patients with abnormal thyroglobulin levels and negative 131I-dWBS findings.