Glucose metabolites, glutamate and glycerol in malignant glioma tumours during radiotherapy.
Level 4 - case-series / case-control
Prospective case series measuring in vivo tissue metabolites before and during radiotherapy
PubMed 18563297 · doi:10.1007/s11060-008-9625-2
What was done
Thirteen patients with malignant glioma had microdialysis catheters implanted into tumour tissue and peri-tumoural tissue during stereotactic biopsy. Fasting microdialysis samples were collected daily at baseline and during 5 days of radiotherapy delivered at 2 Gy fractions (10 Gy total). Levels of glucose, lactate, pyruvate, glutamate, and glycerol were analysed.
What was found
At baseline, glucose (P = 0.04) and pyruvate (P = 0.023) levels were significantly lower in tumour tissue than in peri-tumoural tissue, while the lactate/pyruvate ratio was significantly higher in tumour tissue (P = 0.022). Tumour levels of lactate, glutamate, and glycerol were higher than peri-tumoural levels, but not statistically significantly. No significant changes in any analysed metabolite were detected across the 5 days of radiotherapy. Numerical concentration values were not reported in the abstract.
Why it matters
This in vivo microdialysis study directly confirms the glycolytic phenotype of human malignant glioma relative to surrounding tissue. It indicates that the initial 10 Gy course of radiotherapy does not provoke immediate, measurable metabolic alteration or acute cytotoxic release of glutamate or glycerol.
Limits
The study is limited by a very small sample size (n = 13) and a short follow-up window restricted to the first 5 days of treatment. Microdialysis samples only a very localized tissue region, which may not capture intratumoural heterogeneity. Quantitative concentrations, variability metrics, and clinical outcome correlations were not provided in the abstract.
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