EVALUATION OF FLUORODEOXYGLUCOSE-POSITRON EMISSION TOMOGRAPHIC SCANNING AND ITS ASSOCIATION WITH GLUCOSE-TRANSPORTER EXPRESSION IN MEDULLARY-THYROID CARCINOMA AND PHEOCHROMOCYTOMA - A CLINICAL AND MOLECULAR STUDY

Background, Imaging of metastatic sites of medullary thyroid carcinoma (MTC) is successful in less than 60% of cases of residual or recurren t disease. Positron emission tomography (PET) with [F-18]fluoro-2-deox y-D-glcose (FDG) takes advantage of the fact that malignant tumors are capable of increased uptake and use of glucose, which is mediated by the members of the glucose transporter family of proteins (GLUT 1 thro ugh GLUT 5). Methods. FDG-PET images of 10 patients with recurrent or persistent MTC after primary operation were compared with images by co mputed tomography or magnetic resonance imaging. Identified metastatic lesions were assessed by intraoperative findings and pathology report s. Expression of GLUT 1 through GLUT 5 was examined by Western blot an alysis of tumor tissue from eight of the patients evaluated and an add itional panel of 10 MTCs and seven pheochromocytomas. Results. FDG-PET identified 31 foci of FDG accumulation in 10 patients, and 16 of thes e metastatic sites were resected and confirmed by histologic analysis. Only 11 foci were demonstrated by computed tomographic or magnetic re sonance imaging. None of the glucose transporters examined displayed s ignificant expression. Two pheochromocytomas were successfully imaged by FDG-PET. Conclusions, FDG-PET imaging can be useful in the localiza tion of cervicomediastinal MTC metastases and pheochromocytoma. The In creased glucose uptake in these tumors, as evidenced by FDG-PET, does not appear to be attributable to the expression of the glucose transpo rter proteins GLUT 1 through GLUT 5.