title: Exploring the potential of [11C]choline-PET/CT as a novel imaging biomarker for predicting early treatment response in prostate cancer.
abstract: OBJECTIVE
  The aim of the study was to assess the effects of neoadjuvant androgen deprivation (NAD) and radical prostate radiotherapy with concurrent androgen deprivation (RT-CAD) on prostatic [C]choline kinetics and thus develop methodology for the use of [C]choline-PET/computed tomography (CT) as an early imaging biomarker.
  
  
  METHODS
  Ten patients with histologically confirmed prostate cancer underwent three sequential dynamic [C]choline-PET/CT pelvic scans: at baseline, after NAD and 4 months after RT-CAD. [C]Choline uptake was quantified using the average and maximum standardized uptake values at 60 min (SUV60,ave and SUV60,max), the tumour-to-muscle ratios (TMR60,max) and net irreversible retention of [C]choline at steady state (Kimod-pat).
  
  
  RESULTS
  The combination of NAD and RT-CAD significantly decreased tumour [C]choline uptake (SUV60,ave, SUV60,max, TMR60,max or Kimod-pat) and prostate-specific antigen (PSA) levels (analysis of variance, P<0.001 for all variables). Although the magnitude of reduction in the variables was larger after NAD, there was a smaller additional reduction after RT-CAD. A wide range of reduction in tumour SUV60,ave (38-83.7%) and SUV60,max (22.2-85.3%) was seen with combined NAD and RT-CAD despite patients universally achieving PSA suppression (narrow range of 93.5-99.7%). There was good association between baseline SUV60,max and initial PSA levels (Pearson's r=0.7, P=0.04). The reduction in tumour SUV60,ave after NAD was associated with PSA reduction (r=0.7, P=0.04). This association occurred despite the larger reduction in PSA (94%) compared with SUV60,ave (58%).
  
  
  CONCLUSIONS
  This feasibility study shows that [C]choline-PET/CT detects metabolic changes within tumours following NAD and RT-CAD to the prostate. A differential reduction in [C]choline uptake despite a global reduction in PSA following NAD and RT-CAD could provide prognostic information and warrants further evaluation as an imaging biomarker in this setting.
authors.affiliation: Departments of aSurgery and Cancer bRadiology/Nuclear Medicine, Imperial College London and Imperial College Healthcare NHS Trust cThe PET Imaging Centre, St Thomas' Hospital, London, UK.
authors.forename: Amarnath
authors.initials: A
authors.lastname: Challapalli
authors.forename: Tara
authors.initials: T
authors.lastname: Barwick
authors.forename: Giampaolo
authors.initials: G
authors.lastname: Tomasi
authors.forename: Michael
authors.initials: M
authors.lastname: O' Doherty
authors.forename: Kaiyumars
authors.initials: K
authors.lastname: Contractor
authors.forename: Simon
authors.initials: S
authors.lastname: Stewart
authors.forename: Adil
authors.initials: A
authors.lastname: Al-Nahhas
authors.forename: Kevin
authors.initials: K
authors.lastname: Behan
authors.forename: Charles
authors.initials: C
authors.lastname: Coombes
authors.forename: Eric O
authors.initials: EO
authors.lastname: Aboagye
authors.forename: Stephen
authors.initials: S
authors.lastname: Mangar
mesh_terms: D000728:Androgens / Q000172:deficiency; D002250:Carbon Radioisotopes; D002794:Choline; D006801:Humans; D008297:Male; D064847:Multimodal Imaging; D020360:Neoadjuvant Therapy; D049268:Positron-Emission Tomography; D017430:Prostate-Specific Antigen / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000628:therapy*; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D000728:Androgens; D002250:Carbon Radioisotopes; D017430:Prostate-Specific Antigen; D002794:Choline