title: Role of ¹⁸F-choline PET/CT in suspicion of relapse following definitive radiotherapy for prostate cancer.
abstract: OBJECTIVE
  The aims of the study were (a) to evaluate the diagnostic role, by means of positive detection rate (PDR), of ¹⁸F-choline (CH) positron emission tomography (PET)/CT in patients with prostate cancer treated with radiotherapy, with curative intent, and suspicion of relapse during follow-up, (b) to correlate the PDR with trigger prostate-specific antigen (PSA), (c) to investigate the possible influence of androgen deprivation therapy (ADT) at the time of scan on PDR and (d) to assess distribution of metastatic spread.
  
  
  METHODS
  ¹⁸F-CH PET/CT exams from 46 consecutive patients (mean age 71.3 years, range 51-84 years) with prostate cancer (mean Gleason score 6.4, range 5-8) previously treated by definitive radiotherapy and with suspicion of relapse with negative or inconclusive conventional imaging were retrospectively evaluated. Of the 46 patients, 12 were treated with brachytherapy and 34 with external beam radiation therapy. Twenty-three patients were under ADT at the time of the examination. Trigger PSA was measured within 1 month before the exam (mean value 6.5 ng/ml, range 1.1-49.4 ng/ml). Patients were subdivided into four groups according to their PSA level: 1.0 < PSA ≤ 2.0 ng/ml (11 patients), 2.0 < PSA ≤ 4.0 ng/ml (16 patients), 4.0 < PSA ≤ 6.0 ng/ml (9 patients) and PSA > 6.0 ng/ml (10 patients). Correlation between ADT and PDR was investigated as well as between PSA and distribution of metastatic spread.
  
  
  RESULTS
  The overall PDR of ¹⁸F-CH PET/CT was 80.4% (37/46 patients), increasing with the increase of trigger PSA. PDR of ¹⁸F-CH PET/CT is not influenced by ADT (p = 0.710) even if PET performed under ADT demonstrated an overall higher PDR (82.6%). The majority of the patients (59%, 22/37 patients) showed local relapse only, confined to the prostatic bed; 22% of the PET/CT-positive patients (8/37 patients) showed distant relapse only (bone localizations in all of them), while the remaining 19% (7/37 patients) showed both local and distant (lymph node and bone) spread.
  
  
  CONCLUSIONS
  ¹⁸F-CH PET/CT showed a high overall detection rate (80%), proportional to the trigger PSA (both for local and distant relapse) not influenced by ADT. ¹⁸F-CH PET/CT is proposed as a first-line imaging procedure in restaging prostate cancer patients primarily treated with radiotherapy.
authors.affiliation: Department of Nuclear Medicine, PET/CT Centre, Santa Maria della Misericordia Hospital, Via Tre Martiri 140, 45100 Rovigo, Italy.
authors.forename: Sotirios
authors.initials: S
authors.lastname: Chondrogiannis
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Marzola
authors.forename: Alice
authors.initials: A
authors.lastname: Ferretti
authors.forename: Anna Margherita
authors.initials: AM
authors.lastname: Maffione
authors.forename: Lucia
authors.initials: L
authors.lastname: Rampin
authors.forename: Gaia
authors.initials: G
authors.lastname: Grassetto
authors.forename: Cristina
authors.initials: C
authors.lastname: Nanni
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Colletti
authors.forename: Domenico
authors.initials: D
authors.lastname: Rubello
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy; D002794:Choline / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy; D019275:Radiopharmaceuticals; D012008:Recurrence; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; C516370:fluoromethylcholine; D017430:Prostate-Specific Antigen; D002794:Choline