Abstract
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Objectives Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as well as PET of αvβ3-expression and glucose metabolism provide functional and molecular information on tumor biology in living organisms. These non-invasive quantitative data might be useful for pre-therapeutic stratification and response evaluation to targeted therapies. We therefore evaluated the relationship of these imaging signals in cancer patients.
Methods 13 patients with primary or metastasized cancer (NSCLC n=9; others n=4) were examined with DCE-MRI and PET using [18F]Galacto-RGD and [18F]FDG. In malignant lesions (n=15) different regions of interest (ROI’s) were defined (n=30) based upon the heterogeneity of tracer uptake by using dedicated imaging software. The area under the initial part of the Gd-DTPA concentration-time curve (IAUGC) as well as the relative blood-volume (rBV) and the relative blood-flow (rBF) were estimated from the DCE-MRI and correlated with standardized-uptake-values (SUV’s) from PET.
Results Biologically active tumor regions with both high uptake of [18F]Galacto-RGD (SUV=3.1±0.4) and [18F]FDG (SUV=6.8±0.5) show higher functional MRI data (IAUGC=0.37±0.04 mM*s, rBF=88.9±16.8 ml/min/100g, rBV=25.4±2.6 ml/100g) as compared to areas with low uptake (SUV [18F]Galacto-RGD=1.3±0.1, SUV [18F]-FDG=2.3±0.3, IAUGC=0.15±0.03 mM*s (p<0.01), rBF=47.4±20.8 ml/min/100g, rBV=11.9±2.5 ml/100g (p<0.01)). Regarding different tumor regions, a moderate but significant correlation between IAUGC vs. [18F]Galacto-RGD-PET (r=0.41; p<0.05) and all functional MRI parameters vs. [18F]FDG-PET (r=0.37-0.54; p<0.05) was noted.
Conclusions In tumor areas with low biological activity, perfusion is restricted. However, in biologically active areas, there is a wide variability of perfusion parameters. These data suggest that in active tumor areas, perfusion, αvβ3 expression and glucose metabolism are largely independent variables of tumor biology