The diagnostic usefulness of FDG-PET/CT in detecting tumor recurrence not evident in whole body I131 scan in differentiated thyroid carcinoma

Objective: Patients with differentiated thyroid carcinoma (DTC) have generally an encouraging prognosis, however, some patients develop an increasing level of serum thyroglobulin (Tg) without detection of a recurrent tumor using conventional imaging tools such as the iodine-131 whole-body scanning (I131 scan). The objective of our study was to evaluate the clinical significance of [F18]-FDG-PET/CT in detection of tumor recurrence or metastases, in comparison to conventional imaging such as the I131 scan.Patients and methods: Between January 2013 and June 2013, [18F]-FDG-PET/CT examination was done for 12 DTC patients with elevated thyroglobulin levels and who did not show any pathological lesions when conventional imaging modalities were used. All involved patients had undergone total thyroidectomy, and who had been followed-up by whole body iodine scan [F18]-FDG PET/CT data were evaluated for detecting recurrent DTC lesions in study patients and compared with those of other radiological and/or cytological investigations.Results: Five of 12 patients (41.6 %) showed pathological [F18]-FDG uptake in the absence of abnormal uptake in whole body iodine scan.Conclusion: [F18]-FDG-PET/CT affords a valuable diagnostic method in detection of recurrence or metastasis in patients with DTC who are tumor-free on conventional imaging studies with high Tg levels