Target Analysis of Volatile Organic Compounds in Exhaled Breath for Lung Cancer Discrimination from Other Pulmonary Diseases and Healthy Persons

Abstract

The aim of the present study was to investigate the ability of breath analysis to distinguish lung cancer (LC) patients from patients with other respiratory diseases and healthy people. The population sample consisted of 51 patients with confirmed LC, 38 patients with pathological computed tomography (CT) findings not diagnosed with LC, and 53 healthy controls. The concentrations of 19 volatile organic compounds (VOCs) were quantified in the exhaled breath of study participants by solid phase microextraction (SPME) of the VOCs and subsequent gas chromatography-mass spectrometry (GC-MS) analysis. Kruskal–Wallis and Mann–Whitney tests were used to identify significant differences between subgroups. Machine learning methods were used to determine the discriminant power of the method. Several compounds were found to differ significantly between LC patients and healthy controls. Strong associations were identified for 2-propanol, 1-propanol, toluene, ethylbenzene, and styrene (p-values < 0.001–0.006). These associations remained significant when ambient air concentrations were subtracted from breath concentrations. VOC levels were found to be affected by ambient air concentrations and a few by smoking status. The random forest machine learning algorithm achieved a correct classification of patients of 88.5% (area under the curve—AUC 0.94). However, none of the methods used achieved adequate discrimination between LC patients and patients with abnormal computed tomography (CT) findings. Biomarker sets, consisting mainly of the exogenous monoaromatic compounds and 1- and 2- propanol, adequately discriminated LC patients from healthy controls. The breath concentrations of these compounds may reflect the alterations in patient’s physiological and biochemical status and perhaps can be used as probes for the investigation of these statuses or normalization of patient-related factors in breath analysis.

Benzene, toluene, ethylbenzene, and xylene: Current analytical techniques and approaches for biological monitoring

“…In these techniques, GC-FID [131,132,134,137] or GC-MS [129,133,135,136,[138][139][140] have been used. Different media are used for collection/adsorption of exhaled air, including solid sorbents [132,133,135,136,140], Haldane-Priestly tubes [141], SPME fibers [138,139,142], Tedlar bags [128,129,131,135,142], or canisters [143,144]. In some studies, a breath sampling tube and direct analysis has been developed [137].…”

“…In some studies, a breath sampling tube and direct analysis has been developed [137]. Sample preparation methods include solvent extraction [145], thermal desorption/ cryofocussing step prior to chromatographic analysis [35,136], headspace analysis [135] and SPME [138,139,142]. In recent years, SPME has been emerged as the most common method for the preparation of exhaled air samples.…”

“…During the last two decades, SPME has been used for the determination of BTEX in exhaled-air samples [138,139,142]. Some authors used this technique specifically to measure only one of BTEX [138,139], whereas simultaneous determination of two or more of them has also been reported [142]. In these studies, exhaled air samples are collected on Tedlar bags and then the SPME is used for the adsorption of the analytes.…”

“…In these studies, exhaled air samples are collected on Tedlar bags and then the SPME is used for the adsorption of the analytes. For instance, in a more recent study, Koureas et al used SPME technique for the determination of 19 VOCs, including benzene, toluene and ethyl benzene in exhaled air samples [142]. Briefly, exhaled air samples are collected in Tedlar ® bags and then an SPME manual holder with a 75 µm Carboxen-polydimethylsiloxane (CAR/PDMS)coated fused silica fiber is used for adsorption of the analytes.…”

“…The adsorption is performed for 25 min at room temperature followed by the desorption process for 5 min at 270°C. A same fiber is used for approximately 100 injections [142]. The characteristics of the SPME procedures in different studies are shown in Table 6.…”