title: Non-invasive assessment of inter-and intrapatient variability of integrin expression in metastasized prostate cancer by PET.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.|Current address: Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany.
authors.forename: Ambros J
authors.initials: AJ
authors.lastname: Beer
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.|Current address: Department of Nuclear Medicine, Rostock University Medical Centre, 18057 Rostock, Germany.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Schwarzenböck
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.|Current address: Department of Urology, Klinikum Konstanz, 78464 Konstanz, Germany.
authors.forename: Niko
authors.initials: N
authors.lastname: Zantl
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.|Current address: Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Souvatzoglou
authors.affiliation: Department of Urology, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Maurer
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Watzlowik
authors.affiliation: Institute for Advanced Study (IAS) and Center of Integrated Protein Science (CIPSM), Department Chemie, Technische Universität München, 85747 Garching, Germany.
authors.forename: Horst
authors.initials: H
authors.lastname: Kessler
authors.affiliation: Institute for Radiopharmaceutical Chemistry, Technische Universität München, 85748 Garching, Germany.
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Wester
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany.|Current address: Department of Nuclear Medicine, Rostock University Medical Centre, 18057 Rostock, Germany.
authors.forename: Bernd Joachim
authors.initials: BJ
authors.lastname: Krause
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D039302:Integrin alphaVbeta3 / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic; D049268:Positron-Emission Tomography / Q000379:methods*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D019275:Radiopharmaceuticals; D012189:Retrospective Studies
chemical_list: C572955:18F-RGD-K5; D039302:Integrin alphaVbeta3; D010456:Peptides, Cyclic; D019275:Radiopharmaceuticals
keywords: PET; angiogenesis; integrins; prostate cancer; αvβ3