An electronic nose in the discrimination of patients with non-small cell lung cancer and COPD

Summary 

Background

Exhaled breath contains thousands of gaseous volatile organic compounds (VOCs) that may be used as non-invasive markers of lung disease. The electronic nose analyzes VOCs by composite nano-sensor arrays with learning algorithms. It has been shown that an electronic nose can distinguish the VOCs pattern in exhaled breath of lung cancer patients from healthy controls. We hypothesized that an electronic nose can discriminate patients with lung cancer from COPD patients and healthy controls by analyzing the VOC-profile in exhaled breath.

Methods

30 subjects participated in a cross-sectional study: 10 patients with non-small cell lung cancer (NSCLC, [age 66.4±9.0, FEV₁ 86.3±20.7]), 10 patients with COPD (age 61.4±5.5, FEV₁ 70.0±14.8) and 10 healthy controls (age 58.3±8.1, FEV₁ 108.9±14.6). After 5min tidal breathing through a non-rebreathing valve with inspiratory VOC-filter, subjects performed a single vital capacity maneuver to collect dried exhaled air into a Tedlar bag. The bag was connected to the electronic nose (Cyranose 320) within 10min, with VOC-filtered room air as baseline. The smellprints were analyzed by onboard statistical software.

Results

Smellprints from NSCLC patients clustered distinctly from those of COPD subjects (cross validation value [CVV]: 85%; M-distance: 3.73). NSCLC patients could also be discriminated from healthy controls in duplicate measurements (CVV: 90% and 80%, respectively; M-distance: 2.96 and 2.26).

Conclusion

VOC-patterns of exhaled breath discriminates patients with lung cancer from COPD patients as well as healthy controls. The electronic nose may qualify as a non-invasive diagnostic tool for lung cancer in the future.

Abbreviations: CDA, canonical discriminant analysis, CVV, cross validation value, FEV₁, forced expiratory volume in 1 second, FVC, forced vital capacity, GC–MS, gas chromatography–mass spectrometry, M-distance, Mahalanobis distance, NSCLC, non-small cell lung cancer, PCA, principal component analysis, VOCs, volatile organic compounds

Keywords: Biomarkers, Lung cancer, Electronic nose, Exhaled breath, COPD, Volatile organic compounds