Clinical Significance of FDG Single-Photon Emission Computed Tomography: Computed Tomography in the Diagnosis of Head and Neck Cancers and Study of Its Mechanism

Abstract

The metabolic changes of malignant cells are earlier than these of morphology. (18)F-fluorodeoxyglucose (FDG) single-photon emission computed tomography (SPECT)-computed tomography (CT) systems provide functional and anatomic images that could significantly improve its diagnostic capability. The molecular mechanisms of increased FDG uptake are still not fully understood. The correlation between FDG uptake and the expression of Glut in various tumor cells is still under debate. Further study is necessary to correlate increased FDG uptake by tumors with their Glut-1 and Glut-3 expression, which will lead to a better understanding and interpretation of SPECT-CT imaging. In this study, we, therefore, investigated in patients with head and neck carcinoma (HNC) the relationship between tumor FDG accumulation and the mRNA expression and protein expression of Glut-1 and Glut-3. Overall, 25 patients with HNC who underwent SPECT-CT imaging and CT or magnetic resonance imaging (MRI) studies were performed between April 2002 and March 2004. Then, the mRNA and protein expression of Glut-1 and Glut-3 in these 25 surgical or biopsied samples were studied with HNC to determine the correlate increased FDG uptake by tumors with their Glut-1 and Glut-3 expression. Visual analysis of (18)F-FDG SPECT-CT gave sensitivity, specificity, and accuracy levels of 100%, 62.5%, and 88%, respectively. The tumor-to-background (T/B) ratios were 94.1%, 87.5%, and 92.0% for (18)F-FDG SPECT/CT, and 64.7%, 50.0%, and 60.0% for CT and MRI. This indicates that (18)F-FDG SPECT-CT is superior to CT and MRI. Significant correlation was found between FDG and Glut-1 mRNA or Glut-1 protein (p < 0.001). There was no correlation between T/B ratio and Glut-3 mRNA (r = 0.14, p > 0.01). (18)F-FDG SPECT-CT can be as a prospective tool that can judge the malignancy or benignity of head and neck tumor, stage and classify the tumor, distinguish recurrence or necrosis or fibrosis of the tumor after treatment by surgery or radiotherapy, and detect unknown primary tumor. Glut-1 may largely mediate basal glucose transport in HNC cells.