Valutazione diagnostica post-chirurgica di pazienti con carcinoma tiroideo differenziato: confronto tra ecografia, scintigrafia con iodio-131 e PET con fluoro-18 fluorodesossiglucosio.

Objective. The aim of this study was to compare the results of ultrasound (US), “whole-body” scintigraphy with iodine-131 (WBS) and PET with fluorine-18 deoxyglucose (FDG-PET) in patients with differentiated thyroid carcinoma (DTC) during the post-surgical follow-up. Materials and methods. Thirteen patients (3M, 10F) were evalueted by neck US, WBS and FDG-PET; all patients had near-total thyroidectomy. In each patient 6 anatomic regions (right and left thyroid beds, right and left cervical areas, right and left up-clavear compartments) were investigated for a total of 78 anatomic regions; distant metastases have been considered as a different group in the analysis and were investigated by WBS and FDG-PET. Imaging findings were compared with standard reference data such as: biopsy (n=4) or clinical-radiological (n=9) results. Results. In the neck, US, FDG-PET and WBS showed concordant results in the majority (91%) of sites of which 70 with no lesions, while in a patient with left cervical metastatic lymph node imaging results were concordant for abnormal findings; in the remaining 9% (n=7) of cases, imaging results were discordant; in particular, tumor lesions were detected only by US (n=3), by US and WBS (n=1) and only by FDG-PET (n=3). The detection of distant metastases by FDG-PET and WBS was concordant in the majority (77%) of patients as normal images (n=9), while in a case imaging result were concordant for the presence of tumor lesion. In the last three patients the results were discordant; in particular, in two patients only WBS detected distant metastases, while in the last patient only FDG-PET showed tumor lesion. Conclusions. Results of our work show a fundemental role of US for the evaluation of the neck in patient affected by DTC during the post-surgical follow-up. WBS is useful to determine the differentiation of tumor lesions, for the identification of the residual thyroid gland and for the search of distant metastases. FDG-PET has an important role in cases of undifferentiated DTC in which WBS and thyreoglobulin assay are not able to detect tumor lesions.