title: ADC texture--an imaging biomarker for high-grade glioma?
abstract: OBJECTIVE
  Survival for high-grade gliomas is poor, at least partly explained by intratumoral heterogeneity contributing to treatment resistance. Radiological evaluation of treatment response is in most cases limited to assessment of tumor size months after the initiation of therapy. Diffusion-weighted magnetic resonance imaging (MRI) and its estimate of the apparent diffusion coefficient (ADC) has been widely investigated, as it reflects tumor cellularity and proliferation. The aim of this study was to investigate texture analysis of ADC images in conjunction with multivariate image analysis as a means for identification of pretreatment imaging biomarkers.
  
  
  METHODS
  Twenty-three consecutive high-grade glioma patients were treated with radiotherapy (2 Gy/60 Gy) with concomitant and adjuvant temozolomide. ADC maps and T1-weighted anatomical images with and without contrast enhancement were collected prior to treatment, and (residual) tumor contrast enhancement was delineated. A gray-level co-occurrence matrix analysis was performed on the ADC maps in a cuboid encapsulating the tumor in coronal, sagittal, and transversal planes, giving a total of 60 textural descriptors for each tumor. In addition, similar examinations and analyses were performed at day 1, week 2, and week 6 into treatment. Principal component analysis (PCA) was applied to reduce dimensionality of the data, and the five largest components (scores) were used in subsequent analyses. MRI assessment three months after completion of radiochemotherapy was used for classifying tumor progression or regression.
  
  
  RESULTS
  The score scatter plots revealed that the first, third, and fifth components of the pretreatment examinations exhibited a pattern that strongly correlated to survival. Two groups could be identified: one with a median survival after diagnosis of 1099 days and one with 345 days, p = 0.0001.
  
  
  CONCLUSIONS
  By combining PCA and texture analysis, ADC texture characteristics were identified, which seems to hold pretreatment prognostic information, independent of known prognostic factors such as age, stage, and surgical procedure. These findings encourage further studies with a larger patient cohort.
authors.affiliation: Department of Radiation Sciences, Radiation Physics, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Brynolfsson
authors.affiliation: Computational Life Science Cluster (CLiC), Department of Chemistry, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Nilsson
authors.affiliation: Department of Radiation Sciences, Oncology, Umeå University, Umeå SE-901 87, Sweden and Regionalt Cancercentrum Stockholm, Karolinska Universitetssjukhuset, Solna, Stockholm SE-102 39, Sweden.
authors.forename: Roger
authors.initials: R
authors.lastname: Henriksson
authors.affiliation: Department of Radiation Sciences, Radiation Physics, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Jón
authors.initials: J
authors.lastname: Hauksson
authors.affiliation: Department of Radiation Sciences, Radiation Physics, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Karlsson
authors.affiliation: Department of Radiation Sciences, Radiation Physics, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Garpebring
authors.affiliation: Department of Radiation Sciences, Diagnostic Radiology, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Richard
authors.initials: R
authors.lastname: Birgander
authors.affiliation: Computational Life Science Cluster (CLiC), Department of Chemistry, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Trygg
authors.affiliation: Department of Radiation Sciences, Radiation Physics, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Tufve
authors.initials: T
authors.lastname: Nyholm
authors.affiliation: Department of Radiation Sciences, Oncology, Umeå University, Umeå SE-901 87, Sweden.
authors.forename: Thomas
authors.initials: T
authors.lastname: Asklund
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D018906:Antineoplastic Agents, Alkylating / Q000627:therapeutic use; D001921:Brain / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D059186:Chemoradiotherapy, Adjuvant; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000627:therapeutic use; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D018450:Disease Progression; D005500:Follow-Up Studies; D005910:Glioma / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008875:Middle Aged; D015999:Multivariate Analysis; D060787:Neoplasm Grading; D025341:Principal Component Analysis; D011379:Prognosis; D016019:Survival Analysis; D000077204:Temozolomide; D016896:Treatment Outcome
chemical_list: D018906:Antineoplastic Agents, Alkylating; D003606:Dacarbazine; D000077204:Temozolomide