Differentiation between hypoxic and non-hypoxic experimental tumors by dynamic contrast-enhanced magnetic resonance imaging

Background and purpose: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been suggested to be a useful method for detecting tumor hypoxia. In this study, we investigated whether DCE-MRI can differentiate between hypoxic and non-hypoxic experimental tumors. Materials and methods: Three tumor models with hypoxic tissue and three tumor models without hypoxic tissue were subjected to DCE-MRI. Parametric images of K-trans (the volume transfer constant of Gd-DTPA) and v(e) (the fractional distribution volume of Gd-DTPA) were produced by pharmacokinetic analysis of the DCE-MRI series. Tumor oxygenation status was assessed by using a radiobiological assay and a pimonidazole-based immunohistochemical assay. Tumor response to fractionated irradiation (six fractions of 2 Gy in 60 h) was measured in vitro by using a clonogenic assay. Results: Tumors with hypoxic regions were more resistant to radiation treatment than were tumors without hypoxia. K-trans was significantly higher for radiation sensitive tumors without hypoxia than for radiation resistant tumors with hypoxic regions, whereas v(e) did not differ significantly between non-hypoxic and hypoxic tumors. Conclusion: This study supports the clinical attempts to establish DCE-MRI as a noninvasive method for providing useful biomarkers for personalized radiation therapy. (C) 2011 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 98 (2011) 360-364