Comparison of simplified quantitative analyses of FDG uptake

Quantitative analysis of [ 18F]-fluoro-deoxyglucose (FDG) uptake is important in oncologic positron emission tomography (PET) studies to be able to set an objective threshold in determining if a tissue is malignant or benign, in assessing response to therapy, and in attempting to predict the aggressiveness of an individual tumor. The most common method used today for simple, clinical quantitation is standardized uptake value (SUV). SUV is normalized for body weight. Other potential normalization factors are lean body mass (LBM) or body surface area (BSA). More complex quantitation schemes include simplified kinetic analysis (SKA), Patlak graphical analysis (PGA), and parameter optimization of the complete kinetic model to determine FDG metabolic rate (FDGMR). These various methods were compared in a group of 40 patients with colon cancer metastatic to the liver. The methods were assessed by (1) correlation with FDGMR, (2) ability to predict survival using Kaplan-Meier plots, and (3) area under receiver operating characteristic (ROC) curves for distinguishing between tumor and normal liver. The best normalization scheme appears to be BSA with minor differences depending on the specific formula used to calculate BSA. Overall, PGA is the best predictor of outcome and best discriminator between normal tissue and tumor. SKA is almost as good. In conventional PET imaging it is worthwhile to normalize SUV using BSA. If a single blood sample is available, it is possible to use the SKA method, which is distinctly better. If more than one image is available, along with at least one blood sample, PGA is feasible and should produce the most accurate results.