title: Dual-phase (18)F-fluorocholine PET/CT to detect locoregional recurrence of prostate cancer: comparison between each time point of imaging and a summation scan.
abstract: OBJECTIVE
  Prostate carcinoma is a major health problem, and routine imaging shows only modest results in detecting and restaging clinically localized prostate cancer recurrence. Recent studies have shown promise of radiolabeled analogues of choline for positron emission tomography (PET) scans in patients of biochemical recurrence and that sequentially incremental Fluorocholine (FCH) uptake is associated with malignancy, whereas decreasing tracer activity suggests a benign aetiology. However, this pattern of tracer uptake has not been fully validated, and no standardized (18)F-Fluorocholine ((18)F-FCH) scan protocol is in place yet. This study aimed to better define the role of dual-phase (18)F-FCH PET/computed tomography (CT) imaging using retrospective masked reading focusing on detection of locoregional recurrence/metastasis in patients with biochemical failure after definitive local primary treatment.
  
  
  METHODS
  A total of 32 subjects were enrolled during the period 04/2010 to 05/2014 with histologically proven prostate cancer that was treated with curative intent and had biochemical recurrence. Early scans and delayed imaging of the pelvis were graded separately by blinded readers. Final evaluation using the combination of information from dual-phase studies as a "summation scan" was also performed. Maximum standardized uptake value was computed using regions of interest constructed over focal hyperactivity. Calculations were performed using Statistical Product and Service Solutions, Version 20 for Windows. A composite reference consisting of histopathology, correlation with other imaging, or serum prostate specific antigen (PSA) trend with clinical follow-up of at least 6months was used to determine the true disease status of the patient.
  
  
  RESULTS
  Early-phase pelvis imaging sensitivity and specificity were calculated to be 73.1% and 90.9%, respectively. Late-phase pelvis imaging sensitivity and specificity were 80.8% and 100%, respectively. Summation scan sensitivity and specificity were 76.9% and 100%, respectively. The odds ratio of having recurrent disease with an uptrend of SUVmax on dual-phase imaging was 33.3. The optimal cutoff value of PSA was 1.85ng/mL with 80% sensitivity and 62.5% specificity.
  
  
  CONCLUSIONS
  Single late-phase FCH PET/CT imaging is a reliable scan modality which can detect sites of disease at low levels of PSA which still fulfil the criteria of biochemical recurrence. This will allow clinicians to identify sites for potential biopsy or start locoregional treatment.
authors.affiliation: Department of Nuclear Medicine and PET, Singapore General Hospital, Outram Road, Singapore, 169608.
authors.forename: Aaron Kian Ti
authors.initials: AK
authors.lastname: Tong
authors.affiliation: Epidemiology Department, Singapore General Hospital, Outram Road, Singapore 169608.
authors.forename: Zoe Xiaozhu
authors.initials: ZX
authors.lastname: Zhang
authors.affiliation: Department of Nuclear Medicine and PET, Singapore General Hospital, Outram Road, Singapore, 169608.
authors.forename: Sumbul
authors.initials: S
authors.lastname: Zaheer
authors.affiliation: Department of Nuclear Medicine and PET, Singapore General Hospital, Outram Road, Singapore, 169608. Electronic address: sean.yan.x.x@singhealth.com.sg.
authors.forename: Xuexian Sean
authors.initials: XS
authors.lastname: Yan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002794:Choline / Q000031:analogs & derivatives* / Q000494:pharmacology; D005462:Fluorine Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D012372:ROC Curve; D012189:Retrospective Studies
chemical_list: D005462:Fluorine Radioisotopes; C514960:fluorocholine; D002794:Choline
keywords: Fluorocholine; Positron emission tomography; Prostate carcinoma; Prostate specific antigen