BackgroundThe integrin αvβ3 plays an important role in angiogenesis and tumor cell metastasis, and is currently being evaluated as a target for new therapeutic approaches. Several techniques are being studied to enable noninvasive determination of αvβ3 expression. We developed [18F]Galacto-RGD, a 18F-labeled glycosylated αvβ3 antagonist, allowing monitoring of αvβ3 expression with positron emission tomography (PET).Methods and FindingsHere we show by quantitative analysis of images resulting from a small-animal PET scanner that uptake of [18F]Galacto-RGD in the tumor correlates with αvβ3 expression subsequently determined by Western blot analyses. Moreover, using the A431 human squamous cell carcinoma model we demonstrate that this approach is sensitive enough to visualize αvβ3 expression resulting exclusively from the tumor vasculature. Most important, this study shows, that [18F]Galacto-RGD with PET enables noninvasive quantitative assessment of the αvβ3 expression pattern on tumor and endothelial cells in patients with malignant tumors.ConclusionsMolecular imaging with [18F]Galacto-RGD and PET can provide important information for planning and monitoring anti-angiogenic therapies targeting the αvβ3 integrins and can reveal the involvement and role of this integrin in metastatic and angiogenic processes in various diseases.

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Purpose: The integrin a v h 3 plays a key role in angiogenesis and tumor cell metastasis and is therefore an important target for new therapeutic and diagnostic strategies. We have developed [18 F]Galacto-RGD, a highly a v h 3 -selective tracer for positron emission tomography (PET). Here, we show, in man, that the intensity of [ 18 F]Galacto-RGD uptake correlates with a v h 3 expression. Experimental Design: Nineteen patients with solid tumors (musculoskeletal system, n = 10; melanoma, n = 4; head and neck cancer, n = 2; gliobastoma, n = 2; and breast cancer, n = 1) were examined with PET using [

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