Non-invasive assessment of inter-and intrapatient variability of integrin expression in metastasized prostate cancer by PET

PURPOSE - Due to the high expression of the integrin αvβ3 not only on endothelial cells, but also on mature osteoclasts and prostate cancer cells, imaging of osseous metastases with αvβ3-targeted tracers seems promising.

However, little is known about the patterns of αvβ3-expression in metastasized prostate cancer lesions in-vivo. Thus we evaluated the uptake of the αvβ3-specific PET tracer [18F]Galacto-RGD for assessment of bone metastases in prostate cancer patients.

RESULTS - [18F]Galacto-RGD PET identified 58/74 bone-lesions (detection rate of 78.4%) and lymph node metastases in 2/5 patients. The SUVmean was 2.12+/-0.94 (range 0.70-4.38; tumor/blood 1.36+/-0.53; tumor/muscle 2.82+/-1.31) in bone-lesions and 2.21+/-1.18 (range 0.75-3.56) in lymph node metastases. Good visualization and detection of bone metastases was feasible due to a low background activity of the surrounding normal bone tissue.

METHODS - 12 patients with known metastasized prostate cancer according to conventional staging (including bone-scintigraphy and contrast-enhanced CT; median PSA 68.63 ng/ml, range 3.72-1935) were examined with PET after i.v.-injection of [18F]Galacto-RGD. Two blinded nuclear-medicine physicians evaluated the PET-scans in consensus concerning lesion detectability. Volumes-of-interest were drawn in the PET-scans over all metastases defined by conventional staging (maximum of 11 lesions/patient), over the left ventricle, liver and muscle and standardized-uptake-values (SUVs) were calculated.

CONCLUSIONS - Our data show generally elevated uptake of [18F]Galacto-RGD in bone metastases from prostate cancer with a marked inter- and intrapatient variability. While [18F]Galacto-RGD PET is inferior to bone scintigraphy for detection of osseous metastases, it might be valuable in patient screening and monitoring of αvβ3-targeted therapies due to the high variability of αvβ3-expression.

Oncotarget. 2016 Apr 06 [Epub ahead of print]

Ambros J Beer, Sarah M Schwarzenböck, Niko Zantl, Michael Souvatzoglou, Tobias Maurer, Petra Watzlowik, Horst Kessler, Hans-Jürgen Wester, Markus Schwaiger, Bernd Joachim Krause

Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany., Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany., Department of Urology, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany., Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany., Department of Urology, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany., Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany., Institute for Advanced Study (IAS) and Center of Integrated Protein Science (CIPSM), Department Chemie, Technische Universität München, 85747 Garching, Germany., Institute for Radiopharmaceutical Chemistry, Technische Universität München, 85748 Garching, Germany., Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany., Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.

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