FDG UPTAKE, GLUT-1 GLUCOSE-TRANSPORTER AND CELLULARITY IN HUMAN PANCREATIC TUMORS

We previously reported that grading of GLUT-1 glucose transporter expr ession was related closely to FDG accumulation in FDG PET in human can cers. But in this strong GLUT-1 expression group, there was an enormou s range of standardized uptake values (SUVs) within them. Methods: To evaluate other factors determining the FDG PET uptake, FDG PET was per formed in 36 preoperative patients (mean age 62.0 yr) suspected of hav ing pancreatic tumors, including 33 malignant and 3 benign neoplastic tumors. FDG uptake at 50 min after injection of 185 MBq F-18-FDG with > 5 hr fasting condition was semiquantitatively analyzed as SUVs, The GLUT-1 expression was studied by immunohistochemistry of paraffin sect ions from these tumors after the operation using the antiGLUT-1 antibo dy. The number of tumor cells within a 5- x 5-mm square was counted ma nually using x200 magnification photographs and was graded immunohisto chemically as strong, weak or negative. Results: In all 36 cases there were 3 cases of GLUT-1 negative, 8 of GLUT-1 weak positive and 25 of GLUT-1 strong positive. In all cases, the total number of tumor cells had no significant value for SUVs, Among 33 GLUT-1 positive cases, the number of GLUT-1 positive tumor cells correlated significantly with S UVs (p < 0.01). Only in 25 strong grade cases, the number of GLUT-I st rong positive tumor cells had a more significant Value for SUVs (p < 0 .005). Computational multivariate analysis using multiple regression f or SUVs was performed evaluating the five variables as follows: tumor size, GLUT-1 immunohistochemical grading, number of total tumor cells, number of total GLUT-1 positive tumor cells and number of GLUT-1 stro ng positive cells. This analysis revealed that only the variable, the number of GLUT-1 strong positive cells, had a significant regression c oefficient for SUVs (standard regression coefficient = 0.855, p < 0.00 01). Conclusion: These data indicate that GLUT-1 expression plays an e ssential role in higher FDG accumulation in pancreatic tumor FDG PET, and the cellularity has a significant influence on SUVs only in the co ndition of GLUT-1 strong positive expression.