Correlation of intra-tumor 18F-FDG uptake heterogeneity indices with perfusion CT derived parameters in colorectal cancer

Abstract

Methods: Thirty patients with proven colorectal cancer prospectively underwent integrated 18F-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 18F-FDG PET metabolically active tumor volume as well as with uptake heterogeneity for patients with stage III/IV tumors (|ρ|:0.66 to 0.78; p-value<0.02).

Conclusion: The positive correlation found with tumor blood flow indicates that intra-tumor heterogeneity of 18F-FDG PET accumulation reflects to some extent tracer distribution and consequently indicates that 18F-FDG PET intra-tumor heterogeneity may be associated with physiological processes such as tumor vascularization.

Figure 1. Heterogeneity analysis process.

Illustration of heterogeneity analysis process: in upper an example of tumor (PET/CT with transverse, coronal and sagittal view), at the bottom: illustration of the FLAB delineation after a manual ROI selection that allows heterogeneity analysis.

Figure 2. Correlation between PET heterogeneity and BF.

Scatter diagrams with regression line (solid line) and associated 95% CI (curves above and below regression line represented upper and lower bounds of 95% CI) showing the correlation of BF with A) IV (|ρ| = 0.75, 95%CI: 0.35 to 0.92, p = 0.02), B) local homogeneity (|ρ| = 0.78, 95%CI: 0.40 to 0.93, p = 0.01), C) MATV (|ρ| = 0.71, 95%CI: 0.26 to 0.90, p = 0.05) in stage III/IV tumors.