Correlation of Intra-Tumor 18F-FDG Uptake Heterogeneity Indices with Perfusion CT Derived Parameters in Colorectal Cancer

Application of textural features analysis to 18F-fluorodeoxyglucose (F-18-FDG) positron emission tomography (PET) images has been used to characterize intra-tumor uptake heterogeneity and has been shown to reflect disease outcome. A current hypothesis is that F-18-FDG uptake heterogeneity may reflect the physiological tracer uptake related to tumor perfusion. The purpose of our study was to investigate the correlations between intra-tumor uptake heterogeneity and vascular parameters derived from dynamic contrast enhanced (DCE) computed tomography (CT) obtained from an integrated F-18-FDG PET/perfusion CT examination. Methods: Thirty patients with proven colorectal cancer prospectively underwent integrated F-18-FDG PET/DCE-CT to assess the metabolic-flow phenotype. Both CT blood flow parametric maps and PET images were analyzed. Correlations between PET heterogeneity and perfusion CT were assessed by Spearman's rank correlation analysis. Results: Blood flow visualization provided by DCE-CT images was significantly correlated with F-18-FDG PET metabolically active tumor volume as well as with uptake heterogeneity for patients with stage III/IV tumors (|rho|:0.66 to 0.78; p-value < 0.02). Conclusion: The positive correlation found with tumor blood flow indicates that intra-tumor heterogeneity of F-18-FDG PET accumulation reflects to some extent tracer distribution and consequently indicates that F-18-FDG PET intra-tumor heterogeneity may be associated with physiological processes such as tumor vascularization.