Evaluation of experimental liver tumors using fluorine-18-2-fluoro-2-deoxy-D-glucose PET

Japanese white rabbits transplanted with VX2 liver tumors are considered to be a suitable experimental model for the evaluation of therapeutic modalities. However, there has been no adequate method of assessing the changes of tumor metabolism during treatment. In the present study, 15 rabbits with VX2 liver tumors were examined by PET using 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG). After an intravenous injection of 18F-FDG, serial arterial blood sampling was performed. One hour after tracer injection, small pieces of normal liver tissue and tumor tissue were excised to determine radioactivity. Dynamic PET images were obtained in 11 of the tumor-bearing rabbits, and tumor enzyme activities were determined in six rabbits. Fluorine-18-FDG uptake by the VX2 liver tumors was 3.5 +/- 0.9 times higher than that by the normal liver tissue; so good contrast between tumor and normal liver tissue was achieved on PET scans. The enzyme activity study showed that VX2 tumors had increased levels of hexokinase and pyruvate kinase activity, suggesting an increase of glycolysis. We conclude that transplanted VX2 liver tumors could be appropriately evaluated by 18F-FDG PET.