Comparison of FDG and FLT PET/CT Imaging Based on Human Non-Small Cell Lung Carcinoma Tumor Size in a Small Animal Model

Our goal was to investigate FDG and FLT uptake based on tumor size and the correlation with Ki-67 staining in an Non-Small Cell Lung Carcinoma (NSCLC) xenograft model. A549 human NSCLC cells were subcutaneously implanted into the flanks of nine nude rats. Standardized Uptake Value (SUV) parameters were obtained from FDG and FLT PET/CT images, including SUVmax, SUVmean, tumor to Non-Tumor Ratio (TNR), and Coefficient Of Variation (COV). SUVmax was higher in FDG PET than in FLT PET imaging (P=0.039). Significant correlations of tumor size with SUVmax, TNR, and COV were observed in FDG imaging (r=0.852, P=0.004; r=0.676, P=0.046; r=0.817, P=0.007), but no such correlations were found in FLT imaging (r=0.195, P=0.615; r=0.419, P=0.261; r=0.117, P=0.764). There were significant correlations of the Ki-67 index with SUVmax, TNR, and COV in FLT imaging (r=0.866, P=0.003; r=0.745, P=0.021; r=0.721, P=0.029), but no such correlations in FDG imaging (r=0.478, P=0.193; r=0.478, P=0.193; r=0.617, P=0.077). Our data demonstrated that FDG uptake was better visualized in the tumor and correlated significantly better with tumor size compared with FLT in an NSCLC xenograft model. The tumor heterogeneity on FDG PET correlated well with tumor size, while no correlation was found for FLT.