Thyroid cancer: 18F-Fluoro-2-Deoxy-D-Glucose positron emission tomography (an overview)

Thyroid carcinomas are fairly uncommon and include a broad range of disease types: 94% are differentiated thyroid carcinoma (DTC), 5% are medullary thyroid carcinoma (MTC), and the remaining 1% are anaplastic thyroid carcinoma (ATC). DTCs are derived from the follicular epithelial cells and are either papillary thyroid carcinoma or follicular thyroid carcinoma. MTC is a calcitonin and carcinoembryonic antigen (CEA) secreting neuroendocrine tumor of the parafollicular C-cells of the thyroid. ATC is a very aggressive tumor with poor prognosis characterized by extended local invasion and high frequency of distant metastases at the time of initial diagnosis. Positron emission tomography (PET) using 18F-fluoro-2-deoxy-D-glucose (FDG) as the radiotracer depicts cancer sites based on their increased glucose metabolism. The normal thyroid shows low avidity for FDG. The enhanced ability of thyroid cancers to transport and accumulate glucose is the basis for the use of FDG-PET to identify malignant tumors and metastases. More precisely, the increased FDG accumulation is based on an increased expression of glucose transporters (GLUT), together with an increase of hexokinase activity and a decreased activity of phosphatase seen in most types of tumors. The technique is increasingly used in cancer care because the molecular and metabolic mechanisms underlying the FDG uptake are completely independent of associated structural characteristics, resulting in a superior diagnostic specificity, and because metabolic changes precede structural changes, increasing its sensitivity for early disease stages and its potential for early assessment of the post-therapeutic effects. © 2008 Elsevier Inc.SCOPUS: ch.b