A review suggests that electronic noses which analyse exhaled breath have a high sensitivity and specificity for the detection of cancer
Electronic noses (e-noses) have been found to have a high level of diagnostic accuracy for the detection of cancer in exhaled breath according to a systematic review and meta-analysis by a group of Dutch researchers.
Volatile organic compounds (VOC) represent the end products of human metabolism and which can be excreted in breath, urine, and faeces. As a result, VOC can be very useful as markers of diseases and given that sampling is both non-invasive and painless, it is ideal for both clinicians and patients. Exhaled breath samples can be analysed using a combination of gas-chromatography and mass spectrometry (GS-MS) and this approach has been used to identify a specific profile of organic compounds that can be indicative of a malignancy. For example, one study has suggested that there is a specific profile of markers for ovarian cancer, whereas another revealed how VOCs exhibited significant differences between nodular goitre patients and normal controls, papillary thyroid carcinoma patients and normal controls. While GC-MS systems are expensive, enoses rely on the binding of the organic volatile components to sensors within the device and which generates a measurable electrical response. However, none of the electronic noses are currently used in clinical practice but could be of value although there has not been a systematic evaluation of the utility of these devices.
Consequently, the Dutch team sought to examine the diagnostic performance of currently available enoses for the diagnosis of cancer in exhaled breath samples and assessed the devices in terms of the sensitivity and specificity derived from an analysis of the receiver operating characteristic curve.
Electronic noses and detection of cancer
A total of 52 publications that included 3,677 patients with cancer were included in the final analysis, all of which were feasibility studies. The number of patients in studies ranged from 10 to 351 and the types of cancer identified included lung, head, neck, gastric, breast, colorectal and prostate. In most studies, patients with cancer were compared with controls, normally healthy volunteers and histopathological analysis was used for diagnostic confirmation.
The pooled sensitivity for all 52 studies was 90% (95% CI 88 – 92%) and the pooled specificity was 87% (95% CI 81 – 92%). However, there was a high degree of heterogeneity for both measures.
The authors noted that many studies did not report on the effect of various endogenous or exogenous factors that could affect the breath profile such as smoking and co-morbidities. They concluded that while electronic noses appeared to be reasonably accurate for the detection of cancer, there was a need for adequately powered studies to establish the value of the technology as part of a patient’s diagnostic work-up.
Scheepers MHMC et al. Diagnostic Performance of Electronic Noses in Cancer Diagnoses Using Exhaled Breath: A Systematic Review and Meta-analysis JAMA Netw Open 2022