Fig. 4: Differentially abundant extracellular metabolites in the enhancing glioma, non-enhancing glioma, and adjacent brain comparisons.

Wilcoxon signed-rank tests and fold-changes were calculated between (a) enhancing tumour vs. brain (n = 9 paired catheters), (b) enhancing versus non-enhancing tumour (n = 7 paired catheters), and (d) non-enhancing tumour versus brain (n = 7 paired catheters) were utilised to construct a volcano plot (cut-offs for significance: p-value ≤ 0.05; FC ≥ 2). The normalised peak areas for the top four most differentially abundant extracellular metabolites in enhancing tumour vs. brain are shown in (c) for the 9 cases, including the peak area in non-enhancing tumour for the seven patients for whom this catheter was available. See Table 2 for significant metabolites in each comparison (E/B, E/NE, and NE/B). 2-O-MA = 2-O-methylascorbic acid, DMTPA = 2,3-dihydroxy-5-methylthio-4-pentenoic acid, G-3-P=glycerol-3-phosphate, GAA guanidinoacetate; GPC glycerophosphocholine, GPG glycerophosphorylglycerol, NAA n-acetylaspartate; NAAG n-acetylaspartylglutamate, NANA n-acetylneuraminate.