title: MRI versus ⁶⁸Ga-PSMA PET/CT for gross tumour volume delineation in radiation treatment planning of primary prostate cancer.
abstract: OBJECTIVE
  Multiparametric magnetic resonance imaging (mpMRI) is widely used in radiation treatment planning of primary prostate cancer (PCA). Focal dose escalation to the dominant intraprostatic lesions (DIPL) may lead to improved PCA control. Prostate-specific membrane antigen (PSMA) is overexpressed in most PCAs. (68)Ga-labelled PSMA inhibitors have demonstrated promising results in detection of PCA with PET/CT. The aim of this study was to compare (68)Ga-PSMA PET/CT with MRI for gross tumour volume (GTV) definition in primary PCA.
  
  
  METHODS
  This retrospective study included 22 patients with primary PCA analysed after (68)Ga-PSMA PET/CT and mpMRI. GTVs were delineated on MR images by two radiologists (GTV-MRIrad) and two radiation oncologists separately. Both volumes were merged leading to GTV-MRIint. GTVs based on PET/CT were delineated by two nuclear medicine physicians in consensus (GTV-PET). Laterality (left, right, and left and right prostate lobes) on mpMRI, PET/CT and pathological analysis after biopsy were assessed.
  
  
  RESULTS
  Mean GTV-MRIrad, GTV-MRIint and GTV-PET were 5.92, 3.83 and 11.41 cm(3), respectively. GTV-PET was significant larger then GTV-MRIint (p = 0.003). The MRI GTVs GTV-MRIrad and GTV-MRIint showed, respectively, 40 % and 57 % overlap with GTV-PET. GTV-MRIrad and GTV-MRIint included the SUVmax of GTV-PET in 12 and 11 patients (54.6 % and 50 %), respectively. In nine patients (47 %), laterality on mpMRI, PET/CT and histopathology after biopsy was similar.
  
  
  CONCLUSIONS
  Ga-PSMA PET/CT and mpMRI provided concordant results for delineation of the DIPL in 47 % of patients (40 % - 54 % of lesions). GTV-PET was significantly larger than GTV-MRIint. (68)Ga-PSMA PET/CT may have a role in radiation treatment planning for focal radiation to the DIPL. Exact correlation of PET and MRI images with histopathology is needed.
authors.affiliation: Department of Radiation Oncology, University Medical Center Freiburg, Robert-Koch Straße 3, 79106, Freiburg, Germany. constantinos.zamboglou@uniklinik-freiburg.de.|German Cancer Consortium (DKTK), Partner Site Freiburg, Heidelberg, Germany. constantinos.zamboglou@uniklinik-freiburg.de.
authors.forename: Constantinos
authors.initials: C
authors.lastname: Zamboglou
authors.affiliation: Department of Nuclear Medicine, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Gesche
authors.initials: G
authors.lastname: Wieser
authors.affiliation: Department of Radiation Oncology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Hennies
authors.affiliation: Department of Radiology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Irene
authors.initials: I
authors.lastname: Rempel
authors.affiliation: Department of Radiation Oncology, University Medical Center Freiburg, Robert-Koch Straße 3, 79106, Freiburg, Germany.|German Cancer Consortium (DKTK), Partner Site Freiburg, Heidelberg, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Kirste
authors.affiliation: Department of Radiology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Soschynski
authors.affiliation: Department of Radiation Oncology, University Medical Center Freiburg, Robert-Koch Straße 3, 79106, Freiburg, Germany.
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Rischke
authors.affiliation: Department of Radiation Oncology, University Medical Center Freiburg, Robert-Koch Straße 3, 79106, Freiburg, Germany.|German Cancer Consortium (DKTK), Partner Site Freiburg, Heidelberg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Fechter
authors.affiliation: Department of Urology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Cordula A
authors.initials: CA
authors.lastname: Jilg
authors.affiliation: Department of Radiology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Langer
authors.affiliation: German Cancer Consortium (DKTK), Partner Site Freiburg, Heidelberg, Germany.|Department of Nuclear Medicine, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Philipp T
authors.initials: PT
authors.lastname: Meyer
authors.affiliation: German Cancer Consortium (DKTK), Partner Site Freiburg, Heidelberg, Germany.|Department of Radiology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Bock
authors.affiliation: Department of Radiation Oncology, University Medical Center Freiburg, Robert-Koch Straße 3, 79106, Freiburg, Germany.|German Cancer Consortium (DKTK), Partner Site Freiburg, Heidelberg, Germany.
authors.forename: Anca-Ligia
authors.initials: AL
authors.lastname: Grosu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004492:Edetic Acid / Q000031:analogs & derivatives; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides; D009942:Organometallic Compounds; D000072078:Positron Emission Tomography Computed Tomography; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D047368:Tumor Burden
chemical_list: D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D009842:Oligopeptides; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid
keywords: MRI; PSMA; Prostate cancer; Radiation therapy