The Value of Positron Emission Tomography/Computerized Tomography Imaging in the Restaging of Differentiated Thyroid Cancers and Evaluation of its Association with Thyroglobulin Levels

Sait Sager*, Rana Kaya Doner, Fatma Arzu Gortan, Ozge Vural Topuz, Resit Akyel, Cihan Gündogan, Gamze Tatar, Serkan Teksoz, Kerim Sonmezoglu

Purpose: Recently, there have been an increasing number of studies indicating that Florine-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is a sensitive method in the evaluation of thyroid cancer. This retrospective study aims to assess the value of FDG PET/CT in the evaluation of thyroid cancer and determine the association between serum thyroglobulin (Tg) levels and FDG PET/CT.

Methods: We reviewed FDG PET/CT images of 104 patients with differentiated thyroid cancer (DTC) (28 men, 76 women) whose: (1) iodine-131 (131I) whole-body scanning (WBS) was negative but had elevated Tg levels or (2) Tg level was low, but showed abnormal findings using various imaging methods.

Results: The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of FDG PET/CT findings were found to be 95.92%, 87.27%, 87.04%, 96.00%, and 91.35%, respectively. The best Tg cut-off value was found to be 10.4 ng/ml. In the Tg level <10.4 ng/ml group, the sensitivity, specificity, PPV, NPV, and accuracy of FDG PET/CT were found to be 94.12%, 91.30%, 88.89%, 95.45%, and 92.50%, respectively. In the Tg level ≥10.4 ng/ml group, sensitivity, specificity, PPV, NPV, and accuracy of FDG PET/CT exams were found to be 96.88%, 84.38%, 86.11%, 96.43%, and 90.63%, respectively.

Conclusion: The best predictive Tg cut-off value for FDG PET/CT is not yet to be determined. Since FDG PET/CT can identify residual disease and metastatic foci in cases that lack the ability of 131I accumulation, it should be included in algorithms for DTC follow-up. FDG PET/CT seems to be valuable imaging method in the evaluation of patients with highly elevated serum Tg levels and abnormal lesions identified using different imaging modalities. Furthermore, it has potential utility in the elimination of active foci that are present, and in assessing optimal decision making during follow-up. 

Keywords: Thyroid cancer; Thyroglobulin; I-131 Scintigraphy; FDG PET/CT

Published on: Oct 14, 2015 Pages: 40-47

Full Text PDF Full Text HTML DOI: 10.17352/ijcem.000009
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