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.
Patients and 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.
Keywords: CD133; glioblastoma multiforme; radiotherapy; stem cells; survival.