title: Posttreatment Apparent Diffusion Coefficient Changes in the Periresectional Area in Patients with Glioblastoma.
abstract: BACKGROUND
  Although targeted by radiotherapy, recurrence in glioblastoma occurs mainly periresectionally owing to tumor infiltration. An increase in the apparent diffusion coefficient (ADC) has been shown in the large high-T2 area on magnetic resonance imaging posttreatment; however, until now ADC has not been investigated directly in the more relevant periresectional area.
  
  
  METHODS
  Histogram analysis was used to assess periresectional ADC values in patients with glioblastoma postradiotherapy versus preradiotherapy. Periresectional ADC values starting at 0-5 mm in 5-mm increments up to 20-25 mm were extracted and compared using 2-way repeated-measurements analysis of variance.
  
  
  RESULTS
  Mean ADC values directly adjacent to the resection area (0-5 mm) were significantly higher postradiotherapy compared with preradiotherapy (P = .017). ADC values in the 0- to 5-mm region were also higher than those in 5- to 10-, 10- to 15-, and 15- to 20-mm regions (P < .05). Regional standard deviations in ADC values were higher postradiotherapy compared with preradiotherapy for the 0- to 5-mm region up to the 15- to 20-mm region, inclusive (P < .05); however, Cox regression analysis showed no survival benefits from the increased ADC in the 0- to 5-mm region postradiotherapy.
  
  
  CONCLUSIONS
  Increased ADC values, representing a decrease in infiltrative tumor load, were demonstrated in a limited direct periresectional area. This finding adds to previous studies evaluating ADC response in the larger high-T2 area in relation to survival.
authors.affiliation: University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands. Electronic address: a.van.der.hoorn@umcg.nl.
authors.forename: Anouk
authors.initials: A
authors.lastname: van der Hoorn
authors.affiliation: University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Jiun-Lin
authors.initials: JL
authors.lastname: Yan
authors.affiliation: University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Larkin
authors.affiliation: University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Natalie R
authors.initials: NR
authors.lastname: Boonzaier
authors.affiliation: University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Matys
authors.affiliation: University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Price
mesh_terms: D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality / Q000628:therapy*; D015331:Cohort Studies; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005909:Glioblastoma / Q000000981:diagnostic imaging* / Q000401:mortality / Q000628:therapy*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D012044:Regression Analysis; D016019:Survival Analysis; D016896:Treatment Outcome; D047368:Tumor Burden
keywords: Apparent diffusion coefficient; Brain tumor; Glioblastoma; Magnetic resonance imaging; Treatment response