title: (68)Ga-PSMA PET/CT for restaging recurrent prostate cancer: which factors are associated with PET/CT detection rate?
abstract: OBJECTIVE
  To assess the association between PSA levels, PSA kinetics and other factors and a pathological (68)Ga-PSMA PET/CT scan in patients with recurrent prostate cancer (rPCa) with biochemical relapse (BR) after radical therapy.
  
  
  METHODS
  Seventy consecutive rPCA patients referred for (68)Ga-PSMA PET/CT, matching all the following criteria, were retrospectively evaluated: (a) previous radical prostatectomy or primary radiotherapy with curative intent; (b) BR or persisting high PSA levels after primary treatment; and (c) complete clinical and imaging information. The mean ± SD PSA level was 3.5 ± 5.3 ng/mL (median 1.7, range 0.2 - 32.2 ng/mL), the mean ± SD PSA doubling time (PSAdt) was 6.5 ± 5.5 months (median 5.5, range 1.3 - 31.6 months), and the mean ± SD PSA velocity was 7.9 ± 20.5 (median 2.1, range 0.2 - 147.5 ng/mL/year). Statistical analysis was performed to assess which factors were associated with the detection of rPCa on (68)Ga-PSMA PET/CT.
  
  
  RESULTS
  (68)Ga-PSMA PET/CT was positive in 52 of 70 patients (74.2%). In 30 patients (42.8%) lesions limited to the pelvis were detected. Distant lesions were observed in 8 of patients (11.4%). Local plus systemic lesions were detected in 14 patients (20%). PSA level (p = 0.017) and PSAdt (p = 0.0001) were significantly different between PET-positive patients (higher PSA level, shorter PSAdt) and PET-negative patients (lower PSA, longer PSAdt). ROC analysis showed that PSAdt 6.5 months and PSA 0.83 ng/mL were optimal cut-off values. In multivariate analysis PSAdt was associated with (68)Ga-PSMA PET/CT positivity. (68)Ga-PSMA PET/CT was positive in 17 of 20 patients (85%) with PSA <2 ng/mL and PSAdt <6.5 months, and in 3 of 16 patients (18.7%) with PSA <2 ng/mL and PSAdt ≥6.5 months.
  
  
  CONCLUSIONS
  The great potential of (68)Ga-PSMA PET/CT in patients with rPCa and BR was confirmed. PSA and PSAdt were valuable predictors of pathological (68)Ga-PSMA PET/CT findings.
authors.affiliation: Department of Nuclear Medicine, Medizinische Universität Innsbruck, Anichstraße 35, A-6020, Innsbruck, Austria, francesco.ceci83@gmail.com.
authors.forename: Francesco
authors.initials: F
authors.lastname: Ceci
authors.forename: Christian
authors.initials: C
authors.lastname: Uprimny
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nilica
authors.forename: Llanos
authors.initials: L
authors.lastname: Geraldo
authors.forename: Dorota
authors.initials: D
authors.lastname: Kendler
authors.forename: Alexander
authors.initials: A
authors.lastname: Kroiss
authors.forename: Jasmin
authors.initials: J
authors.lastname: Bektic
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Horninger
authors.forename: Peter
authors.initials: P
authors.lastname: Lukas
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
authors.forename: Paolo
authors.initials: P
authors.lastname: Castellucci
authors.forename: Stefano
authors.initials: S
authors.lastname: Fanti
authors.forename: Irene J
authors.initials: IJ
authors.lastname: Virgolini
mesh_terms: D000328:Adult; 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; D064847:Multimodal Imaging; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging* / Q000473:pathology; D009367:Neoplasm Staging; D009842:Oligopeptides; D049268:Positron-Emission Tomography; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D009842:Oligopeptides; D019275:Radiopharmaceuticals; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid