Objective:

Assess whether rapid mass spectrometry can distinguish glioma from nontumor brain tissue and classify gliomas by molecular subtype and grade, including in tissue relevant to surgical margins.

Approach:

• Samples: Researchers analyzed 86 human brain specimens: 78 gliomas and eight nontumor samples.
• Method: A sterile syringe plunger collected tissue for syringe touch spray tandem mass spectrometry. The analysis compared metabolite ratios and took approximately three minutes.
• Margin assessment: Researchers tested mixtures of tumor and normal brain tissue to examine how metabolite ratios changed with tumor-cell proportion.

Key Findings:

• The N-acetylaspartate-to-carnitine ratio distinguished glioma from nontumor tissue with 97% sensitivity, 100% specificity, and 98% accuracy against clinical diagnoses.
• Ratios involving 2-hydroxyglutarate separated 13 IDH-mutant from 24 IDH-wild-type samples in the study cohort.
• Several metabolite ratios separated grade 2 from grade 4 tumors and grade 3 from grade 4 tumors in the analyzed samples.
• In tissue mixtures, ratios involving 2-hydroxyglutarate, glutamate, and carnitine generally changed with tumor-cell proportion. Some mixtures with substantial tumor content fell below the cutoff derived from tumor-core tissue.

Interpretation:

The researchers described the method as a potential source of molecular information during surgery, particularly at tumor margins, rather than a replacement for current standard-of-care procedures.

Limitations:

• The study analyzed 86 specimens, including only eight nontumor samples.
• Some mixtures containing substantial tumor content fell below the tumor-core cutoff, indicating that this threshold may miss cancer in heterogeneous margins.

Conclusion:

The study reported rapid differentiation and classification of glioma tissue using metabolite ratios, while noting a potential challenge in applying tumor-core thresholds to surgical margins.

Sources:

• Article context; study published in Proceedings of the National Academy of Sciences