title: Impact of CD133 positive stem cell proportion on survival in patients with glioblastoma multiforme.
abstract: BACKGROUND
  The aim of the study was to assess the impact of CD133-positive (CD133+) cancer stem cell proportions on treatment results of glioblastoma multiforme (GBM) patients.
  
  
  METHODS
  Patients with GBM (n = 42) received postoperative radiotherapy (± chemotherapy). Surgically excised GBM tissue sections were immunohistochemically examined for CD133 expression. The proportions of CD133+ GBM cells were determined (%). The proportion of CD133+ GBM stem cells was established by 2 independent researchers whose results were in good accordance (R = 0.8, p < 0.01). Additionally, CD133 expression levels were correlated with patients overall survival.
  
  
  RESULTS
  The proportion of CD133+ cells varied between patients, being from 0.5% to 82%. Mean and median proportions of CD133+ cells of the entire study group were 33% ± 24% (mean ± SD) and 28%, respectively. Clinical data do not support the association between higher proportion of stem cells and the aggressiveness of GBM. Median survival time of the study group was 10.0 months (95% CI 9.0-11.0). The survival time clearly depended on the proportion of CD133+ cells (log rank test, p = 0.02). Median survival times for patients with low (< median) and high (≥ median) proportion of CD133+ cells were 9.0 months (95% CI 7.6-10.5) and 12.0 months (95% CI 9.3-14.7), respectively. In multivariate analysis, the proportion of CD133+ cells emerged as a significant independent predictor for longer overall survival (HR 2.0, 95% CI 1.0-3.8, p = 0.04).
  
  
  CONCLUSIONS
  In patients with higher stem cell proportion, significantly longer survival times after postoperative radiotherapy were achieved. Underlying reasons and possible higher sensitivity of GBM stem cells to fractionated radio-therapy should be clarified in further studies.
authors.affiliation: Faculty of Medicine, University of Tartu, Estonia.
authors.forename: Marju
authors.initials: M
authors.lastname: Kase
authors.forename: Ave
authors.initials: A
authors.lastname: Minajeva
authors.forename: Kristi
authors.initials: K
authors.lastname: Niinepuu
authors.forename: Sandra
authors.initials: S
authors.lastname: Kase
authors.forename: Markus
authors.initials: M
authors.lastname: Vardja
authors.forename: Toomas
authors.initials: T
authors.lastname: Asser
authors.forename: Jana
authors.initials: J
authors.lastname: Jaal
keywords: CD133; glioblastoma multiforme; radiotherapy; stem cells; survival