Impact of CD133+ stem cell proportion on survival in patients with glioblastoma multiforme
Purpose: 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 (%). Additionally, CD133 expression levels were correlated with patients overall survival.
Results: The proportion of CD133+ GBM stem cells was determined by 2 independent researchers whose results were in good accordance (R=0.8, p<0.01). 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. 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).Conclusion: These clinical data do not support the association between higher proportion of stem cells and the aggressiveness of GBM. In contrast, 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 radiotherapy should be clarified in further studies.