A novel approach to non-invasive lung cancer screening via exhaled breath analysis using proton transfer reaction time-of-flight mass spectrometry

Lung cancer (LC) remains a global public health problem. To minimize late diagnosis, new detection techniques are needed. The analysis of volatile organic compounds (VOCs) in human breath (the volatilome) represents a non-invasive alternative to current methods for the early detection of LC. In this study, VOCs were determined in the breath of individuals with LC (N=22) and without LC (non-LC, N=21) using proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). Orthogonal partial least squares discriminant analysis (oPLS-DA) and hierarchical cluster analysis (HCA) were conducted on a subset of 54 VOC ions (out of 180). Twenty-one of the 54 VOC ions were detected in exhaled breath. CH₄O₃H⁺ and C₈H₇NH⁺ were found only in participants without cancer. Among the 19 common ions present in both cohorts, the intensities of 8 ions were statistically different. The LC/non-LC ratios were observed for C₄H₈O₂H⁺, followed by C₃H₄OH⁺, C₂H₂OH⁺, C₂H₃ONH⁺, C₃H₄H⁺, C₃H₂H⁺, C₄H₈H⁺, and C₆H₈H⁺. Spearman correlation analysis could be used to differentiate metabolic processes or pathways between cohorts. Diagnostic ratio is a potential tool to classify individuals with or without lung cancer. This study provides exploratory evidence for exhaled VOCs as potential LC biomarkers and positions them as a complement to current diagnostic pathways, with a potential role in supporting early triage and clinical decision-making.