title: 68Ga-PSMA-11 PET/CT in primary staging of prostate cancer: PSA and Gleason score predict the intensity of tracer accumulation in the primary tumour.
abstract: OBJECTIVE
  Prostate cancer (PC) cells typically show increased expression of prostate-specific membrane antigen (PSMA), which can be visualized by68Ga-PSMA-11 PET/CT. The aim of this study was to assess the intensity of68Ga-PSMA-11 uptake in the primary tumour and metastases in patients with biopsy-proven PC prior to therapy, and to determine whether a correlation exists between the primary tumour-related68Ga-PSMA-11 accumulation and the Gleason score (GS) or prostate-specific antigen (PSA) level.
  
  
  METHODS
  Ninety patients with transrectal ultrasound biopsy-proven PC (GS 6-10; median PSA: 9.7 ng/ml) referred for68Ga-PSMA-11 PET/CT were retrospectively analysed. PET images were analysed visually and semiquantitatively by measuring the maximum standardized uptake value (SUVmax). The SUVmaxof the primary tumour and pathologic lesions suspicious for lymphatic or distant metastases were then compared to the physiologic background activity of normal prostate tissue and gluteal muscle. The SUVmaxof the primary tumour was assessed in relation to both PSA level and GS.
  
  
  RESULTS
  Eighty-two patients (91.1%) demonstrated pathologic tracer accumulation in the primary tumour that exceeded physiologic tracer uptake in normal prostate tissue (median SUVmax: 12.5 vs. 3.9). Tumours with GS of 6, 7a (3+4) and 7b (4+3) showed significantly lower68Ga-PSMA-11 uptake, with median SUVmaxof 5.9, 8.3 and 8.2, respectively, compared to patients with GS >7 (median SUVmax: 21.2; p < 0.001). PC patients with PSA ≥10.0 ng/ml exhibited significantly higher uptake than those with PSA levels <10.0 ng/ml (median SUVmax: 17.6 versus 7.7; p < 0.001). In 24 patients (26.7%), 82 lymph nodes with pathologic tracer accumulation consistent with metastases were detected (median SUVmax: 10.6). Eleven patients (12.2%) revealed 55 pathologic osseous lesions suspicious for bone metastases (median SUVmax: 11.6).
  
  
  CONCLUSIONS
  The GS and PSA level correlated with the intensity of tracer accumulation in the primary tumours of PC patients on68Ga-PSMA-11 PET/CT. As PC tumours with GS 6+7 and patients with PSA values ≤10 ng/ml showed significantly lower68Ga-PSMA-11 uptake,68Ga-PSMA-11 PET/CT should be preferentially applied for primary staging of PC in patients with GS >7 or PSA levels ≥10 ng/ml.
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. christian.uprimny@tirol-kliniken.at.
authors.forename: Christian
authors.identifier: http://orcid.org/0000-0001-5588-3363
authors.initials: C
authors.lastname: Uprimny
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Alexander Stephan
authors.initials: AS
authors.lastname: Kroiss
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
authors.affiliation: Department of Medical Statistics, Informatics and Health Economics, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Josef
authors.initials: J
authors.lastname: Fritz
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: von Guggenberg
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Dorota
authors.initials: D
authors.lastname: Kendler
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Scarpa
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Gianpaolo
authors.initials: G
authors.lastname: di Santo
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Llanos Geraldo
authors.initials: LG
authors.lastname: Roig
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Johanna
authors.initials: J
authors.lastname: Maffey-Steffan
authors.affiliation: Department of Urology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Horninger
authors.affiliation: Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Irene Johanna
authors.initials: IJ
authors.lastname: Virgolini
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004492:Edetic Acid / Q000031:analogs & derivatives; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009842:Oligopeptides; D009942:Organometallic Compounds; D000072078:Positron Emission Tomography Computed Tomography; D017430:Prostate-Specific Antigen / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology*; D011849:Radioactive Tracers; D012189:Retrospective Studies
chemical_list: D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D009842:Oligopeptides; D009942:Organometallic Compounds; D011849:Radioactive Tracers; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid; D017430:Prostate-Specific Antigen
keywords: 68Ga-PSMA-11 PET/CT; Primary staging; Prostate cancer