title: Comparison of standard and delayed imaging to improve the detection rate of [68Ga]PSMA I&T PET/CT in patients with biochemical recurrence or prostate-specific antigen persistence after primary therapy for prostate cancer.
abstract: OBJECTIVE
  The aim of this study was to assess the value of dual-time point imaging in PET/CT for detection of biochemically recurrent or persistent prostate cancer, using the prostate-specific membrane antigen (PSMA) ligand [68Ga]PSMA I&T.
  
  
  METHODS
  240 patients who underwent a [68Ga]PSMA I&T PET/CT in the context of biochemical relapse of prostate cancer were included in this retrospective analysis. Imaging consisted of a standard whole-body PET/CT (1 h p.i.), followed by delayed (3 h p.i.) imaging of the abdomen. PSA-stratified proportions of positive PET/CT results, standardized uptake values and target-to-background ratios were analyzed, and compared between standard and delayed imaging.
  
  
  RESULTS
  The overall detection rates of [68Ga]PSMA I&T PET/CT were 94.2, 71.8, 58.6, 55.9 and 38.9% for PSA levels of ≥2, 1 to <2, 0.5 to <1, >0.2 to <0.5, and 0.01 to 0.2 ng/mL, respectively. Although the target-to-background ratio improved significantly over time (P < 0.0001), the majority (96.6%) of all lesions suggestive of recurrent disease could already be detected in standard imaging. Delayed imaging at 3 h p.i. exclusively identified pathologic findings in 5.4% (10/184) of abnormal [68Ga]PSMA I&T PET/CT scans, and exclusively detected 3.4% (38/1134) of all lesions suggestive of recurrent disease.
  
  
  CONCLUSIONS
  [68Ga]PSMA I&T PET/CT shows high detection rates in patients with prostate-specific antigen persistence or biochemical recurrence of prostate cancer. Delayed imaging can detect lesions with improved contrast compared to standard imaging. However, the impact on detection rates was limited in this study.
authors.affiliation: Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schmuck
authors.affiliation: Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Nordlohne
authors.affiliation: Department of Urology and Urologic Oncology, Hannover Medical School, Hannover, Germany.
authors.forename: Christoph-A
authors.initials: CA
authors.lastname: von Klot
authors.affiliation: Department of Radiation Oncology, Hannover Medical School, Hannover, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Henkenberens
authors.affiliation: Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany.
authors.forename: Jan M
authors.initials: JM
authors.lastname: Sohns
authors.affiliation: Department of Radiation Oncology, Hannover Medical School, Hannover, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Christiansen
authors.affiliation: Pharmaceutical Radiochemistry, Technische Universität München|, Garching, Germany.
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Wester
authors.affiliation: Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany.
authors.forename: Tobias L
authors.initials: TL
authors.lastname: Ross
authors.affiliation: Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Bengel
authors.affiliation: Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany. Derlin.Thorsten@mh-hannover.de.
authors.forename: Thorsten
authors.identifier: http://orcid.org/0000-0002-8786-4105
authors.initials: T
authors.lastname: Derlin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D056831:Coordination Complexes; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods* / Q000592:standards; D017430:Prostate-Specific Antigen / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D012008:Recurrence; D012015:Reference Standards; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: C000615601:68Ga-DOTAGA-(3-iodo-y)fk(Sub-KuE); D056831:Coordination Complexes; D009842:Oligopeptides; D017430:Prostate-Specific Antigen
keywords: Delayed imaging; Detection rate; Dual-phase imaging; PET/CT; PSMA; Prostate cancer