Breath Analysis for Early Detection of Malignant Pleural Mesothelioma: Volatile Organic Compounds (VOCs) Determination and Possible Biochemical Pathways

Abstract

Malignant pleural mesothelioma (MPM) is a rare neoplasm, mainly caused by asbestos exposure, with a high mortality rate. The management of patients with MPM is controversial due to a long latency period between exposure and diagnosis and because of non-specific symptoms generally appearing at advanced stage of the disease. Breath analysis, aimed at the identification of diagnostic Volatile Organic Compounds (VOCs) pattern in exhaled breath, is believed to improve early detection of MPM. Therefore, in this study, breath samples from 14 MPM patients and 20 healthy controls (HC) were collected and analyzed by Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC/MS). Nonparametric test allowed to identify the most weighting variables to discriminate between MPM and HC breath samples and multivariate statistics were applied. Considering that MPM is an aggressive neoplasm leading to a late diagnosis and thus the recruitment of patients is very difficult, a promising data mining approach was developed and validated in order to discriminate between MPM patients and healthy controls, even if no large population data are available. Three different machine learning algorithms were applied to perform the classification task with a leave-one-out cross-validation approach, leading to remarkable results (Area Under Curve AUC = 93%). Ten VOCs, such as ketones, alkanes and methylate derivates, as well as hydrocarbons, were able to discriminate between MPM patients and healthy controls and for each compound which resulted diagnostic for MPM, the metabolic pathway was studied in order to identify the link between VOC and the neoplasm. Moreover, five breath samples from asymptomatic asbestos-exposed persons (AEx) were exploratively analyzed, processed and tested by the validated statistical method as blinded samples in order to evaluate the performance for the early recognition of patients affected by MPM among asbestos-exposed persons. Good agreement was found between the information obtained by gold-standard diagnostic methods such as computed tomography CT and model output.

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

“…These changes in body composition can lead to increased release of deposited compounds and, in our case, of toluene, ethylbenzene, and styrene. It is known that following weight loss, lipophilic organic pollutants are released from adipose tissue into the blood circulation and their increased levels can be detected for a long period [ 32 , 33 , 34 ]. This hypothesis also agrees with our observation that increased levels of monoaromatic compounds are observed in the breath of Ca + and Ca − patients vs. HC in spite of the fact that the concentrations of these compounds were significantly lower in the ambient air of LC sampling in comparison to that for HC sampling room ( Supplementary Figures S9, S13, and S14 ).…”

Breath Analysis: Comparison among Methodological Approaches for Breath Sampling

“…The values related to the difference between the LC breath sample and ambient air sample reported in Figure 2 for these VOCs resulted in higher values than the other data collected from HC breath samples, confirming results obtained in other studies that found these species linked to LC [ 1 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ]. In fact, regarding benzene, for example, several studies focused on breath analysis have demonstrated that this exogenous pollutant usually linked to exposure of tobacco smoke and air pollution, could be possible diagnostic biomarkers of cancer able to discriminate between cancer patients and healthy controls [ 1 , 6 , 7 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ]. It is reasonable considering that patients affected by cancer have been exposed to excessive smoking and/or have experienced continuous occupational exposure by up taking these compounds into the fatty tissues of the body and releasing them into the breath slowly and constantly [ 63 ].…”

“…The procedure was repeated two to three times after 2 to 5 min of rest to fill the entire volume of the inert 3L-Tedlar bags L (Restek, Bellefonte, PA, USA). As reported in a previous study [ 7 ], a statistical analysis based on several experimental sessions was conducted to evaluate the VOCs’ background of Tedlar bags used in this study and the most effective approach to reduce it. This consisted of filling 10 different bags with wet high-purity grade air and measuring the VOCs’ content over the time and in different cleaning conditions.…”

“…Exogenous VOCs are mainly environmental pollutants that are taken up by the body via inhalation and skin adsorption or species absorbed through food ingestion. On the bases of these considerations, several studies demonstrated that the identification of a specific pattern of endogeneous VOCs’ characteristics of a disease is a useful tool for its early diagnosis [ 5 , 6 , 7 ]. However, it is important to consider that changes in VOCs’ profile in human breath could be due to: (a) exogenous VOCs linked to ambient air where breath sampling occurs, (b) environmental exposure to VOCs, (c) confounding factors such as sex, diet, genetics, smoking habits, etc., and (d) differences in VOCs’ diffusion from blood to alveolar air depending on their physic-chemical properties such as polarity, volatility, and solubility in fat [ 8 ].…”

Exhaled Volatile Organic Compounds during Inflammation Induced by TNF-α in Ventilated Rats

“…For example, exhaled gases are potential diagnostic tools for lung cancer [5][6][7], chronic obstructive pulmonary disease [8], and hemorrhagic shock [9]. Breath analysis even allows detecting gastric cancer, differentiating stages of precancerous gastric lesions [10], and helps distinguish between patients with malignant pleural mesothelioma and healthy subjects [11].…”