Using positron emission tomography with [F-18]FDG to predict tumor behavior in experimental colorectal cancer

This study investigates the relationship between FDG uptake as determined b y positron emission tomography (PET) imaging and rates of tumor growth, cel lular GLUT1 transporter density, and the activities of hexokinase and gluco se-6-phosphatase in a solid tumor implant model. Five different human color ectal xenografts of different growth properties were implanted in athymic r ats and evaluated by dynamic F-18-FDG-PET. The phosphorylating and dephosph orylating activities of the key glycolytic enzymes, hexokinase and glucose- 6-phosphatase, were measured in these tumor types by spectrophotometric ass ays and the expression of GLUT1 glucose transporter protein was determined by immunohistochemistry. Correlations among FDG accumulation, hexokinase ac tivity, and tumor doubling time are reported in these colon xenografts. The results indicate that the activity of tumor hexokinase may be a marker of tumor growth rate that can be determined by F-18-FDG-PET imaging. PET scann ing may not only be a useful tool for staging patients for extent of diseas e, but may provide important prognostic information concerning the prolifer ative rates of malignancies.