title: Changes in apparent diffusion coefficient and T2 relaxation during radiotherapy for prostate cancer.
abstract: OBJECTIVE
  To evaluate regional and temporal changes in apparent diffusion coefficient (ADC) and T2 relaxation during radiation therapy (RT) in patients with low and intermediate risk localized prostate cancer.
  
  
  METHODS
  Seventeen patients enrolled on a prospective clinical trial where MRI was acquired every 2 weeks throughout eight weeks of image-guided prostate IMRT (78 Gy/39 fractions). ADC and T2 quantification used entire prostate, central gland, benign peripheral zone, and tumor-dense regions-of-interest, and mean values were evaluated for common response trends.
  
  
  RESULTS
  Overall, the RT responses were greater than volunteer measurement repeatability, and week 6 appeared to be an optimum time-point for early detection. RT effects on the entire prostate were best detected using ADC (5-7% by week 2, P < 0.0125), effects on peripheral zone were best detected using T2 (19% reduction at week 6; P = 0.004) and effects on tumors were best detected using ADC (14% elevation at week 6; P = 0.004).
  
  
  CONCLUSIONS
  ADC and T2 may be candidate biomarkers of early response to RT warranting further investigation against clinical outcomes.
authors.affiliation: Radiation Medicine Program, Princess Margaret Hospital, and Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada. warren.foltz@rmp.uhn.on.ca
authors.forename: Warren D
authors.initials: WD
authors.lastname: Foltz
authors.forename: Andy
authors.initials: A
authors.lastname: Wu
authors.forename: Peter
authors.initials: P
authors.lastname: Chung
authors.forename: Charles
authors.initials: C
authors.lastname: Catton
authors.forename: Andrew
authors.initials: A
authors.lastname: Bayley
authors.forename: Michael
authors.initials: M
authors.lastname: Milosevic
authors.forename: Robert
authors.initials: R
authors.lastname: Bristow
authors.forename: Padraig
authors.initials: P
authors.lastname: Warde
authors.forename: Anna
authors.initials: A
authors.lastname: Simeonov
authors.forename: David A
authors.initials: DA
authors.lastname: Jaffray
authors.forename: Masoom A
authors.initials: MA
authors.lastname: Haider
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ménard
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011446:Prospective Studies; D011467:Prostate / Q000473:pathology* / Q000528:radiation effects*; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D050397:Radiotherapy, Intensity-Modulated; D012306:Risk; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen