title: Residual tumor volume versus extent of resection: predictors of survival after surgery for glioblastoma.
abstract: OBJECTIVE
  The impact of extent of resection (EOR) on survival for patients with glioblastoma (GBM) continues to be a point of debate despite multiple studies demonstrating that increasing EOR likely extends survival for these patients. In addition, contrast-enhancing residual tumor volume (CE-RTV) alone has rarely been analyzed quantitatively to determine if it is a predictor of outcome. The purpose of this study was to evaluate the effect of CE-RTV and T2/FLAIR residual volume (T2/F-RV) on overall survival.
  
  
  METHODS
  A retrospective review of 128 patients who underwent primary resection of supratentorial GBM followed by standard radiation/chemotherapy was undertaken utilizing quantitative, volumetric analysis of pre- and postoperative MR images. The results were compared with clinical data obtained from the patients' medical records.
  
  
  RESULTS
  At analysis, 8% of patients were alive, and no patients were lost to follow-up. The overall median survival was 13.8 months, with a median Karnofsky Performance Scale (KPS) score of 90 at presentation. The median contrast-enhancing preoperative tumor volume (CE-PTV) was 29.0 cm(3), and CE-RTV was 1.2 cm(3), equating to a 95.8% median EOR. The median T2/F-RV was 36.8 cm(3). CE-PTV, CE-RTV, T2/F-RV, and EOR were all statistically significant predictors of survival when controlling for age and KPS score. A statistically significant benefit in survival was seen with a CE-RTV less than 2 cm(3) or an EOR greater than 98%. Evaluation of the volumetric analysis methodology was performed by observers of varying degrees of experience-an attending neurosurgeon, a fellow, and a medical student. Both the medical student and fellow recorded correlation coefficients of 0.98 when compared with the attending surgeon's measured volumes of CE-PTV, while for CE-RTV, correlation coefficients of 0.67 and 0.71 (medical student and fellow, respectively) were obtained.
  
  
  CONCLUSIONS
  CE-RTV and EOR were found to be significant predictors of survival after GBM resection. CERTV was the more significant predictor of survival compared with EOR, suggesting that the volume of residual contrast-enhancing tumor may be a more accurate and meaningful reflection of the pathobiology of GBM.
authors.affiliation: Brain Tumor and Neuro-Oncology Center and Department of Neurosurgery, and.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Grabowski
authors.forename: Pablo F
authors.initials: PF
authors.lastname: Recinos
authors.forename: Amy S
authors.initials: AS
authors.lastname: Nowacki
authors.forename: Jason L
authors.initials: JL
authors.lastname: Schroeder
authors.forename: Lilyana
authors.initials: L
authors.lastname: Angelov
authors.forename: Gene H
authors.initials: GH
authors.lastname: Barnett
authors.forename: Michael A
authors.initials: MA
authors.lastname: Vogelbaum
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000473:pathology* / Q000601:surgery*; D005260:Female; D005909:Glioblastoma / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual / Q000473:pathology; D019635:Neurosurgical Procedures / Q000379:methods*; D015588:Observer Variation; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013534:Survival; D016019:Survival Analysis; D055815:Young Adult
keywords: AIC = Akaike information criterion; AN = attending neurosurgeon; CE-PTV = contrast-enhancing preoperative tumor volume; CE-RTV = contrast-enhancing residual tumor volume; EOR = extent of resection; FEL = fellow; FLAIR = fluid-attenuated inversion recovery; GBM = glioblastoma; KPS = Karnofsky Performance Scale; MPRAGE = magnetization-prepared rapid acquisition gradient echo; MS = medical student; PTV = preoperative tumor volume; SSDI = Social Security Death Index; T2/F-RV = T2/FLAIR residual volume; craniotomy; extent of resection; glioblastoma; oncology; volumetrics