title: The Theranostic PSMA Ligand PSMA-617 in the Diagnosis of Prostate Cancer by PET/CT: Biodistribution in Humans, Radiation Dosimetry, and First Evaluation of Tumor Lesions.
abstract: PET imaging with the prostate-specific membrane antigen (PSMA)-targeted radioligand (68)Ga-PSMA-11 is regarded as a significant step forward in the diagnosis of prostate cancer (PCa). More recently, a PSMA ligand was developed that can be labeled with (68)Ga, (111)In, (177)Lu, and (90)Y. This ligand, named PSMA-617, therefore enables both diagnosis and therapy of PCa. The aims of this evaluation were to clinically investigate the distribution of (68)Ga-PSMA-617 in normal tissues and in PCa lesions as well as to evaluate the radiation exposure by the radioligand in PET imaging.
  
  
  METHODS
  Nineteen patients, most of them with recurrent PCa, were referred for (68)Ga-PSMA-617 PET/CT. The quantitative assessment of tracer uptake of several organs and of 53 representative tumor lesions was performed in 15 patients at 1 and 3 h after injection. In 4 additional patients, the same procedure was conducted at 5 min, 1 h, 2 h, 3 h, 4 h, and 5 h after injection. On the basis of the data for these 4 patients (mean injected dose, 231 MBq), the radiation exposure of a (68)Ga-PSMA-617 PET/CT was identified.
  
  
  RESULTS
  Intense tracer uptake was observed in the kidneys and salivary glands. In 14 of 19 patients (73.7%), at least 1 lesion suspected of being a tumor was detected at 3 h after injection. Of 53 representative tumor lesions selected at 3 h after injection, 47 lesions were visible at 1 h after injection. The mean tumor-to-background ratio for maximum standardized uptake value was 20.4 ± 17.3 (range, 2.3-84.0) at 1 h after injection and 38.2 ± 38.6 (range, 3.6-154.3) at 3 h after injection. The average radiation exposure (effective dose) was approximately 0.021 mSv/MBq.
  
  
  CONCLUSIONS
  Within healthy organs, the kidneys and salivary glands showed the highest (68)Ga-PSMA-617 uptake. The radiation exposure was relatively low. (68)Ga-PSMA-617 shows PCa lesions with high contrast. Images obtained between 2 and 3 h after injection seem to be the best option with regard to radiotracer uptake and tumor contrast. Later images can help to clarify unclear lesions.
authors: Department of Nuclear Medicine, Heidelberg University Hospital, Heidelberg, Germany Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, Heidelberg, Germany a.afshar@gmx.de.
authors: Ali
authors: A
authors: Afshar-Oromieh
authors: Division of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany.
authors: Henrik
authors: H
authors: Hetzheim
authors: Department of Nuclear Medicine, Heidelberg University Hospital, Heidelberg, Germany.
authors: Clemens
authors: C
authors: Kratochwil
authors: Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany.
authors: Martina
authors: M
authors: Benesova
authors: Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany.
authors: Matthias
authors: M
authors: Eder
authors: Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany.
authors: Oliver C
authors: OC
authors: Neels
authors: Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany.
authors: Michael
authors: M
authors: Eisenhut
authors: Division of Radiation Protection and Dosimetry, German Cancer Research Center, Heidelberg, Germany; and.
authors: Wolfgang
authors: W
authors: Kübler
authors: Department of Biostatistics, German Cancer Research Center, Heidelberg, Germany.
authors: Tim
authors: T
authors: Holland-Letz
authors: Department of Nuclear Medicine, Heidelberg University Hospital, Heidelberg, Germany.
authors: Frederik L
authors: FL
authors: Giesel
authors: Department of Nuclear Medicine, Heidelberg University Hospital, Heidelberg, Germany.
authors: Walter
authors: W
authors: Mier
authors: Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany.
authors: Klaus
authors: K
authors: Kopka
authors: Department of Nuclear Medicine, Heidelberg University Hospital, Heidelberg, Germany Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, Heidelberg, Germany.
authors: Uwe
authors: U
authors: Haberkorn
mesh_terms: D000328:Adult; D004151:Dipeptides / Q000627:therapeutic use*; D004492:Edetic Acid / Q000031:analogs & derivatives; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes / Q000627:therapeutic use*; D006573:Heterocyclic Compounds, 1-Ring / Q000627:therapeutic use*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000000981:diagnostic imaging / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides; D009942:Organometallic Compounds / Q000627:therapeutic use*; D049268:Positron-Emission Tomography; D017430:Prostate-Specific Antigen / Q000737:chemistry*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy*; D011874:Radiometry; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D012469:Salivary Glands / Q000000981:diagnostic imaging / Q000378:metabolism; D000068936:Theranostic Nanomedicine; D014018:Tissue Distribution
chemical_list: D004151:Dipeptides; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D006573:Heterocyclic Compounds, 1-Ring; D009842:Oligopeptides; D009942:Organometallic Compounds; C000602389:PSMA-617; D019275:Radiopharmaceuticals; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid; D017430:Prostate-Specific Antigen
keywords: PET/CT; PSMA; dosimetry; positron emission tomography; prostate cancer; prostate-specific membrane antigen