Permeability to macromolecular contrast media quantified by dynamic MRI correlates with tumor tissue assays of vascular endothelial growth factor (VEGF).

PURPOSE: To correlate dynamic MRI assays of macromolecular endothelial permeability with microscopic area-density measurements of vascular endothelial growth factor (VEGF) in tumors. METHODS AND MATERIAL: This study compared tumor xenografts from two different human cancer cell lines, MDA-MB-231 tumors (n=5), and MDA-MB-435 (n=8), reported to express respectively higher and lower levels of VEGF. Dynamic MRI was enhanced by a prototype macromolecular contrast medium (MMCM), albumin-(Gd-DTPA)35. Quantitative estimates of tumor microvascular permeability (K(PS); μl/min × 100 cm(3)), obtained using a two-compartment kinetic model, were correlated with immunohistochemical measurements of VEGF in each tumor.
RESULTS: Mean K(PS) was 2.4 times greater in MDA-MB-231 tumors (K(PS)=58 ± 30.9 μl/min × 100 cm(3)) than in MDA-MB-435 tumors (K(PS)=24 ± 8.4 μl/min × 100 cm(3)) (p<0.05). Correspondingly, the area-density of VEGF in MDA-MB-231 tumors was 2.6 times greater (27.3 ± 2.2%, p<0.05) than in MDA-MB-435 cancers (10.5 ± 0.5%, p<0.05). Considering all tumors without regard to cell type, a significant positive correlation (r=0.67, p<0.05) was observed between MRI-estimated endothelial permeability and VEGF immunoreactivity.
CONCLUSION: Correlation of MRI assays of endothelial permeability to a MMCM and VEGF immunoreactivity of tumors support the hypothesis that VEGF is a major contributor to increased macromolecular permeability in cancers. When applied clinically, the MMCM-enhanced MRI approach could help to optimize the appropriate application of VEGF-inhibiting therapy on an individual patient basis.