Abstract
1473
Objectives: Transport and phosphorylation of FDG in the tumor cells determine primarily the kinetics of the tracer and the accumulation. However, experimental data have shown that angiogenesis may have an impact on the glucose kinetics. This study is focussed on the combined evaluation of PET FDG and angiogenesis related gene expression. Methods: Dynamic PET FDG studies were performed in 25 patients with colorectal tumors within two days prior to surgery. Volumes-of-Interest (VOI) were used to obtain time-dependent tracer concentrations from the tumor region and a reference area. VOIs over the descending aorta were used to retrieve FDG total blood concentration data. A two-tissue-compartment model was fitted to the data and the transport constants k1-k4 as well as the fracional blood volume (vessel density, VB) were calculated using the evaluation software PMOD (PMOD Technologies Ltd., Adliswil, Switzerland). Tumor specimen as well as specimen from the normal colon were obtained by surgery and quantitative gene expression data were obtained by gene array analysis using the U133A gene chip (Affymetrix Inc., Santa Clara,CA,USA). PET and gene array data were evaluated with the GenePET module of PMOD. Results: A quantitative data evaluation was performed in 25 patients, comprising 42 specimen of tumors and normal colon tissue. Angiogenesis related genes were enhanced by a factor of 2.9, when tumors and normal colon were compared. Classification analysis demonstrated that 5 angiogenesis related genes provided the best discrimination between malignancies and reference tissue. The correlation/regression analysis demonstrated significant correlations (p<5 %) for the fractal dimension (heterogeneity of the tracer), k1, and k3. SUV and influx were different only for a group based analysis. Conclusions: Angiogenesis has a significant impact primarily on the kinetic data (k1, k3), and has a minor effect on the global FDG uptake. A detailed analysis of the FDG kinetics can help to classify the grade of angiogenesis in primary colorectal tumors.
- Society of Nuclear Medicine, Inc.