The diagnostic value of 124I-PET in patients with differentiated thyroid cancer

Abstract

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Objectives: Widespread metastastic or recurrent disease in patients with differentiated thyroid cancer (DTC) can be associated with significant morbidity and even mortality. Proper staging and tumor detection is crucial for appropriate therapy management. The purpose of this ongoing prospective study is to evaluate the clinical diagnostic possibility of 124I-PET in patients with advanced DTC and to compare the124I-PET imaging results with the conventional 131I-WBS. Methods: Seventeen patients with histologically proven advanced DTC (T4 or extra-nodal tumor growth or distant metastases) underwent a diagnostic (Dx) 131I-WBS, a 124I-PET and a post-treatment (Pt) 131I-WBS, in the evaluation phase 4 months after ablation. The findings on the 124I-PET scans were compared with the findings on the Dx and Pt 131I-WBS. Results: Five patients had positive findings on both the124I -PET and Pt 131I-WBS , whereas the Dx 131I-WBS were negative. Three of these five still had detectable thyroglobulin (Tg). Two patients had positive findings on all the three scans, but the abnormalities were more clear and extensive on the 124I-PET and were confirmed on the Pt 131I-WBS. These two patients also still had detectable Tg. One patient had negative findings on both the 124I-PET and Dx 131I-WBS, whereas the Pt 131I-WBS showed abnormal uptake in the skull. The Tg of this patient was persistently negative. One patient showed doubtful findings on the 124I-PET, whereas the Dx and Pt 131I-WBS were negative. This patient however still had detectable Tg. In one patient both the 124I-PET and Dx 131I-WBS were negative, the Pt 131I-WBS showed doubtful findings. The Tg of this patient was however negative. Seven patients had negative findings on all the three scans. Five of seven still had detectable Tg. Conclusions: Iodine-124 PET showed more abnormal findings compared to the Dx 131I-WBS, but seems to show comparable findings with the Pt 131I-WBS.