Imaging of integrin avb3 expression in patients with malignant glioma by [18F] Galacto-RGD positron emission tomography
Inhibitors targeting the integrin avb3 are promising new agents currently tested in clinical trials for supplemental therapy of glioblastoma multiforme (GBM). The aim of our study was to evaluate 18F-labeled glycosylated Arg-Gly-Asp peptide ([18F]Galacto-RGD) PET for noninvasive imaging of avb3 expression in patients with GBM, suggesting eligibility for this kind of additional treatment. Patients with suspected or recurrent GBM were examined with [18F]Galacto-RGD PET. Standardized uptake values (SUVs) of tumor hotspots, galea, and blood pool were derived by region-of-interest analysis. [18F]Galacto-RGD PET images were fused with cranial MR images for image-guided surgery. Tumor samples taken from areas with intense tracer accumulation in the [18F]Galacto-RGD PET images and were analyzed histologically and immunohistochemically for avb3 integrin expression. While normal brain tissue did not show significant tracer accumulation (mean SUV, 0.09 6 0.04), GBMs demonstrated significant but heterogeneous tracer uptake, with a maximum in the highly proliferating and infiltrating areas of tumors (mean SUV, 1.6 6 0.5). Immunohistochemical staining was prominent in tumor microvessels as well as glial tumor cells. In areas of highly proliferating glial tumor cells, tracer uptake (SUVs) in the [18F]Galacto-RGD PET images correlated with immunohistochemical avb3 integrin expression of corresponding tumor samples. These data suggest that [18F] Galacto-RGD PET successfully identifies avb3 expression in patients with GBM and might be a promising tool for planning and monitoring individualized cancer therapies targeting this integrin.