Comments on “Pilot Study: Detection of Gastric Cancer From Exhaled Air Analyzed With an Electronic Nose in Chinese Patients”

Dear Editor,

We have read with great interest the article of Schuermans and colleagues, ¹ who reported a pilot study on electronic nose’s ability to distinguish gastric cancer patients from healthy controls.

Electronic noses, or e-noses, are artificial devices composed of sensors that are able to respond to variation of compounds’ concentrations. These compounds, commonly known as volatile organic compounds (VOCs), are mostly related to metabolism and released from cells into bloodstream. Then, the bloodstream carries VOCs to the lungs, where they are exchanged into the exhaled breath. Breath can be collected, for instance, in sterile bags and analyzed with several approaches, which are collectively known as “Breathomics” or “Volatolomics,” the metabolomic study of exhaled air.

In the past 5 years, extensive research has been made on e-nose’s development, as evidenced by more than 400 articles in the literature. E-nose’s ability to detect different type of disease, such as asthma, cystic fibrosis, cirrhotic condition, diabetes, and bacterial infection, had been tested. In the oncological area, e-nose was able to distinguish healthy subjects and patients with lung, prostate, head and neck, breast, and colorectal cancer.

Looking at the literature, the study of Schuermans and colleagues ¹ is one of the few regarding e-nose’s ability to diagnose gastric cancer. Excluding the 2 works cited by the authors, there are also the work of Xu and colleagues in 2013, ² which used nanomaterial-based sensors with an 89% sensitivity and 90% specificity, and the work of Amal and colleagues in 2016, ³ which showed 73% sensitivity and 98% specificity. Even though Schuermans and colleagues’ study was on a limited number of subjects (16 patients with diagnosed gastric carcinoma compared with 28 healthy subjects), the e-nose reached a sensitivity of 81% and a specificity of 71%, with an accuracy of 75%. These 2 parameters indicated, respectively, the test’s ability to correctly classify the patient as diseased or disease-free and allow the calculation of the accuracy, which can be considered as the “efficacy” of the test. The data obtained from this study strengthened the pivotal role of e-nose as a screening tool in medicine and, as suggested by the authors, underline the importance of further studies in a well-selected larger patient population.

Gastric cancer mortality has been estimated to decrease in the coming years; nevertheless, 33 200 new diagnosis have been predicted in Europe for 2018. ⁴ Usually the screening method for high-risk individuals (eg, history of gastric carcinoma or subjects with suspected symptomatology) is a gastroscopy, which allows direct visualization of oncological processes ongoing on the esophagus and stomach. This type of approach is invasive, with the chance of complications and requires highly specialized personnel. In this context, the e-nose fits with appropriate characteristics.

Moreover, breath analysis has already been involved in the monitoring of gastric disease, such as Helicobacter pylori infection, which is also one of the major risk factor for the development of gastric cancer. Monitoring of VOCs’ composition could allow observing variations of the gastric microbiota reflecting cancerous lesions and help improve subjects’ selection, helping decide which patients should undergo further examination. VOCs’ alteration in patients with gastric carcinoma has been evaluated by means of gas chromatography-mass spectrometry; however, this approach is difficult to apply in clinical practice. ⁵

Indeed, the work of Schuermans and colleagues ¹ supports the promising results already published regarding e-nose’s ability to diagnose other pathological conditions and underlines the great interest that this technology is gathering in the scientific community.