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

BACKGROUND: The purpose of this prospective study was to evaluate the clinical diagnostic value of iodine-124 ((124)I)-positron emission tomography (PET) in patients with advanced differentiated thyroid carcinoma (DTC) and to compare the (124)I-PET imaging results with the (131)I whole-body scan (WBS). MATERIALS AND METHODS: Twenty patients with histologically proven advanced DTC (including T4, extra-nodal tumour growth, or distant metastases) underwent diagnostic (131)I-WBS, (124)I-PET scan, and post-treatment (131)I-WBS 4 months after ablation. The findings on the (124)I-PET were compared with the findings on the diagnostic and post-therapeutic (131)I-WBS and were also correlated with radiologic and/or cytological investigations. RESULTS: (124) I-PET vs diagnostic (131) I-WBS. Eleven patients showed uptake on the (124)I-PET. Only 3 of these 11 patients also showed uptake on the diagnostic (131)I scan, but the uptake was more clearly visible and the abnormalities were more extensive on the (124)I-PET. (124) I-PET vs post-treatment (131) I-WBS. Eleven patients showed uptake on the (124)I-PET, which was also visible on the post-treatment scan in nine patients; in the other two patients, no uptake was observed on the post-treatment scan and no anatomical localisation could be confirmed. Two patients showed only uptake on the post-treatment scan without uptake on the (124)I-PET: in one, the uptake was confirmed by MRI, and in the other, no anatomical localisation was found. In seven patients, no uptake was observed on both the scans. CONCLUSION: (124)I-PET proved to be a superior diagnostic tool as compared to low-dose diagnostic (131)I scans and adequately predicted findings on subsequent high-dose post-treatment (131)I scans.