Our nose is capable of detecting more than a trillion different odors despite being equipped with only a few hundred receptors. Even more powerful is the electronic nose which instead of natural olfactory receptors has a series of sensors composed of carbon nanotubes about 100 thousand times smaller than the width of a hair and an electronic ‘brain’ that uses the power of intelligence. artificial.
For years we have been studying how to exploit this power also for the early diagnosis of tumors and some research – such as those conducted by Memorial Sloan Kettering Cancer Center of New York – have already demonstrated efficacy for the detection of pancreatic and ovarian cancers. But more recently, another line of research has also emerged which is to exploit the volatile organic compounds (VOCs) found in our breath to diagnose cancer.
To take stock of the situation is now a meta-analysis that tries to understand what progress has been made and whether this approach can actually make an oncological diagnosis with the electronic nose more concrete.
Breast cancer, mammography sensitivity increases by 11% with Artificial Intelligence
by Irma D’Aria
Why Vocs Can Be Useful
Volatile organic compounds that can be detected in our breath are degradation products of biochemical processes in the human body deriving from hydrocarbons such as formaldehyde, methanol, ethanol, hydrogen sulfate, benzene, acetaldehyde, acetone, toluene, phenols that are produced during metabolic, inflammatory and oxidative stress processes.
The composition of the Vocs we exhale changes as a result of some pathological processes, such as cancer. Due to their low blood solubility, Vocs easily spread to the alveolar area and are subsequently excreted through the breath, allowing for their detection and even linkage with some specific conditions, including cancer.
An easy and non-invasive test
Breath analysis has several advantages over that of other clinical specimens. The breath test is painless and non-invasive. Additionally, unlike blood and urine samples, breath samples require no processing, allowing for immediate analysis and quick results.
The methods for the detection of Vocs
The most accurate method of identifying Vocs is a combination of two tests, gas chromatography and mass spectrometry, indicated by the abbreviation of GC-MS, a highly accurate method that allows for the selective detection of individual Vocs. Previous studies using GC-MS have succeeded in identifying potentially disease-specific VOCs as markers for several malignant tumors. However, this examination takes time and money and can only be performed by qualified experts.
The role of the electronic nose
A relatively new emerging technique for the analysis of Vocs in exhaled breath can be performed through electronic noses. These are portable, inexpensive and easy to use diagnostic tests that can produce fast results.
The detection is possible thanks to the tiny sensors placed inside the electronic noses connected to the Vocs and capable of generating an electronic response that can be measured even if, unlike the GC-MS exam, the electronic noses are not able to identify the individual Voc. Furthermore, the accuracy of these electronic devices is influenced by endogenous and exogenous factors, such as comorbidities, smoking, diet, body mass index and the quality of the ambient air, all factors that can alter the type of Voc detected in the breath.
Diagnostic accuracy in oncology
The detections of the compounds found in our breath thanks to the electronic nose have been extensively analyzed to understand if they can represent a useful tool in oncological diagnosis. The results obtained so far – even if preliminary – are considered promising and encouraging for the high diagnostic precision, but in clinical practice currently no electronic nose is used to detect malignant tumors.
The meta-analysis
There is currently no systematic review available that provides an aggregate analysis of the diagnostic performance of electronic noses for cancer detection. This meta-analysis was conducted on 52 feasibility studies involving a total of 3677 cancer patients with various types of cancers: lung, head and neck, gastric, breast, colorectal, mesothelioma, oral cavity, ovaries and prostate.
How the electronic nose works
The electronic noses most commonly included in experiments to detect VOCs used metal oxide sensors, or quartz or nanomaterials. The most used type of electronic nose was the Cyranose 320 which represents an innovative biomimetic method capable of simulating the human olfactory system in verifying the quality of odors through the use of a system of nano-sensors in combination with specific algorithms of reworking.
The instrument is able to detect volatile organic compounds (VOCs) through the definition of a specific profile: in fact the sample is analyzed by 32 sensors in which the modification of the electrical conductivity with respect to a reference sample is recorded.
The exhaled air contains more than 200 volatile organic substances (VOCs) present in traces, many of which derive from the metabolism of endogenous substances and others from external contamination (xenobiotic compounds) of the exhaled air, represents a new approach for the evaluation of metabolic alterations linked to various diseases, such as lung cancer, asthma and cystic fibrosis.
Noses with 90% sensitivity
“The results of this systematic review – he explains Max Scheepers from the Grow School for Oncology and Developmental Biology at Maastricht University – indicate that electronic noses have relatively high diagnostic accuracy in detecting cancer through exhaled breath. “
At the end of the processing of the aggregated data it was found that the noses have a sensitivity of 90% and a specificity of 87% in detecting cancer. However, the limitation is that these are feasibility studies with small sample sizes, lack of standardization and a high risk of bias. “Multicentric and more significant external validation studies are needed – continues Scheepers – to establish the real potential of electronic noses in the diagnostic analysis of cancer”.