Purpose: [ 18 F]Galacto-RGD has been developed for positron emission tomography (PET)î maging of avh3 expression, a receptor involved in angiogenesis and metastasis. Our aim was to study the feasibility of PET imaging with [ ]Galacto-RGD, static emission scans 60 min post injection from the head to the abdomen (n = 11) and dynamic scans >60 min covering the tumor region (n = 6) for kinetic modeling were acquired. Standardized uptake values (SUV) were measured in tumors, muscle and oral mucosa. Immunohistochemistry was done using an avh3-specific antibody (n = 7). Image fusion with magnetic resonance imaging and/or computed tomography (CT) scans (n = 8) and calculation of tumor subvolumes based on SUVs was done using the iPlan software (BrainLAB).

Our data indicate that [(68)Ga]DOTA-RGD allows monitoring of alphavbeta3 expression. Especially, the much easier radiosynthesis compared to [(18)F]Galacto-RGD would make it an attractive alternative. However, due to higher blood pool activity, [(18)F]Galacto-RGD remains superior for imaging alphavbeta3 expression. Introduction of alternative chelator systems may overcome the disadvantages.

The integrin a v b 3 is a key player in angiogenesis and metastasis. Our aim was to study the uptake patterns of the a v b 3 -selective PET tracer 18 F-galacto-RGD in invasive ductal breast cancer. Methods: Sixteen patients with primary (n 5 12) or metastasized breast cancer (n 5 4) were examined with 18 F-galacto-RGD PET.Standardized uptake values (SUVs) were derived by region-ofinterest analysis, and immunohistochemistry of a v b 3 expression was performed (n 5 5). Results: 18 F-Galacto-RGD PET identified all invasive carcinomas, with SUVs from 1.4 to 8.7 (mean 6 SD, 3.6 6 1.8; tumor-to-blood and tumor-to-muscle ratios, 2.7 6 1.6 and 6.2 6 2.2, respectively). Lymph-node metastases were detected in 3 of 8 patients (mean SUV, 3.3 6 0.8). SUVs in distant metastases were heterogeneous (2.9 6 1.4). Immunohistochemistry confirmed a v b 3 expression predominantly on microvessels (5/5) and, to a lesser extent, on tumor cells (3/5). Conclusion: Our results suggest generally elevated and highly variable a v b 3 expression in human breast cancer lesions. Consequently, further imaging studies with 18 F-galacto-RGD PET in breast cancer patients for assessment of angiogenesis or planning of a v b 3 -targeted therapies are promising.

Inhibitors targeting the integrin alpha(v)beta(3) are promising new agents currently tested in clinical trials for supplemental therapy of glioblastoma multiforme (GBM). The aim of our study was to evaluate (18)F-labeled glycosylated Arg-Gly-Asp peptide ([(18)F]Galacto-RGD) PET for noninvasive imaging of alpha(v)beta(3) expression in patients with GBM, suggesting eligibility for this kind of additional treatment. Patients with suspected or recurrent GBM were examined with [(18)F]Galacto-RGD PET. Standardized uptake values (SUVs) of tumor hotspots, galea, and blood pool were derived by region-of-interest analysis. [(18)F]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 [(18)F]Galacto-RGD PET images and were analyzed histologically and immunohistochemically for alpha(v)beta(3) integrin expression. While normal brain tissue did not show significant tracer accumulation (mean SUV, 0.09 +/- 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 +/- 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 [(18)F]Galacto-RGD PET images correlated with immunohistochemical alpha(v)beta(3) integrin expression of corresponding tumor samples. These data suggest that [(18)F] Galacto-RGD PET successfully identifies alpha(v)beta(3) expression in patients with GBM and might be a promising tool for planning and monitoring individualized cancer therapies targeting this integrin.