The flow-metabolic phenotype of primary colorectal cancer: assessment by integrated 18F-FDG PET/perfusion CT with histopathologic correlation.

Abstract

The aim of this study was to assess the in vivo flow-metabolic phenotype in primary colorectal cancer with integrated (18)F-FDG PET/perfusion CT and its relationship to gold standard histopathologic assessment of angiogenesis and hypoxia. 45 patients (26 male and 19 female; mean age, 67.6 y) with primary colorectal cancer underwent integrated (18)F-FDG PET/perfusion CT, deriving tumor glucose metabolism (maximum standardized uptake value) and regional blood flow. From this cohort, 35 underwent surgery subsequently, without intervening neoadjuvant treatment, allowing histopathologic correlation with tumor stage, CD105 microvessel density, vascular endothelial growth factor (VEGF), glucose transporter protein 1 (Glut-1), and hypoxia-inducible factor 1 expression. The flow-metabolic ratio was significantly lower for tumors with higher VEGF (3.65 vs. 5.98; P = 0.01) or hypoxia-inducible factor 1 expression (3.63 vs. 5.48; P = 0.04) versus tumors with lower expression. There were significant negative correlations between the tumor flow-metabolic ratio and VEGF expression (r = -0.55, P = 0.0008), indicating that tumors with low blood flow but higher metabolism were associated with higher VEGF expression. Flow and metabolism were coupled in higher-stage (stage III/IV) tumors but not lower-stage tumors (stage I/II) (r = 0.47, P = 0.03, vs. r = 0.09, P = 0.65, respectively. Tumors with a low-flow-high-metabolism phenotype demonstrated higher VEGF expression and may reflect a more angiogenic phenotype.