In this study, we examined the in vivo relationship between functional tumor vasculature, determined by dynamic contrast-enhanced (DCE-) MRI, and tumor metabolism, determined by dynamic 18 F-FDG PET, during cytotoxic treatment of patients with colorectal liver metastases. Methods: Twenty-three patients underwent DCE-MRI (using gadolinium dimeglumine) and dynamic 18 F-FDG PET at baseline and after 3 treatment cycles, unless treatment was terminated because of toxicity. Parameters for vasculature

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... (rate constant between extravascular extracellular space and blood plasma [k ep ] and volume transfer constant [K trans ]), extracellular space (v e ), tumor size (the maximal axial diameter of each included lesion [MAD]), and metabolism (glucose metabolic rates [MR glc ]) were derived, and changes during treatment were correlated. Overall survival (OS) and progression-free survival (PFS) served as outcome measures for the predictive abilities of pretreatment parameters and of treatment-related parameter changes. Results: Pretreatment MR glc and MAD were individually predictive for OS and PFS. During treatment, K trans increased significantly, but this increase could not be confirmed in a lesion-by-lesion analysis. MR glc decreased significantly (P , 0.001). No correlations were found for changes in DCE-MRI parameters and DMR glc . No relationship was found between changes in DCE-MRI parameters and OS or PFS. DMR glc was able to predict OS (P 5 0.008) after correction for confounders. Conclusion: The efficacy of cytotoxic chemotherapy assessed by reduction in tumor metabolism does not depend on pretreatment properties of the tumor vasculature determined by DCE-MRI. Cytotoxic chemotherapy does not alter DCE-MRI-derived properties of tumor vasculature but decreases glucose consumption of tumor cells.