Electronic noses show high accuracy for cancer detection
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Electronic noses that detect volatile organic compounds in exhaled breath have emerged as potential tools for cancer detection, but more investigation is needed before they can become part of the diagnostic workup, according to researchers.
Volatile organic compounds (VOCs) are degradation products of biochemical processes in the body, and changes in VOC composition may be indicative of pathologies such as cancer. Because VOCs have low blood solubility, they disperse easily into alveolar air and are expelled through exhaled breath.
Electronic noses, or e-noses, are a relatively new technique in VOC analysis. The portable, inexpensive tests yield fast results, are noninvasive and do not require an accompanying workup.
“Electronic noses are sensing devices that can detect certain odors or flavors,” Max Scheepers, MD, a PhD candidate in the department of surgery at GROW School for Oncology and Developmental Biology at Maastricht University in the Netherlands, told Healio. “E-noses are being investigated in medical research to determine the potential of these devices in the detection of a variety of diseases, including cancer.”
To gain a better understanding of the overall diagnostic accuracy and challenges of using e-noses for cancer detection, Scheepers and colleagues conducted a systematic review of the literature and identified 52 feasibility studies that included a total of 3,677 patients with cancer.
Scheepers and study co-author Zaid Al-Difaie, PhD, a member of the faculty of health, medicine and life sciences at GROW School, spoke with Healio about the findings, published in JAMA Network Open, and the potential role of e-noses in the future of cancer detection.
Healio: How do e-noses detect VOC changes indicative of cancer?
Scheepers: It has been hypothesized that e-noses can detect diseases due to the binding of VOCs to sensors within an e-nose, which generates an electrical response that can then be measured and analyzed. By determining the differences in the VOC pattern of healthy and diseased patients, e-noses could have a potential role in the diagnostic workup of diseases.
Healio: What did your review find as far as the diagnostic accuracy of electronic noses?
Al-Difaie: Our meta-analysis found a high diagnostic accuracy of e-noses for the detection of cancer, with a pooled sensitivity of 90% and specificity of 87%. E-noses showed high diagnostic accuracy for detection of lung cancer, head and neck cancer, and colorectal cancer, although they had a relatively low specificity in detecting colorectal cancer compared with lung and head and neck cancers. The high diagnostic accuracy of e-noses in this study is in line with results of previous reviews that found similar diagnostic performance in detecting cancer in exhaled breath. However, the results of the meta-analysis should be interpreted with caution because of high heterogeneity among studies, a lack of standardization, a high risk for bias found in most studies, and the potential presence of publication bias.
Healio: What might the high heterogeneity and high risk for bias mean in terms of the efficacy of this technology?
Scheepers: The existing e-nose studies generally consist of feasibility studies with small sample sizes. Furthermore, there is a lack of external validation studies to confirm the results. Therefore, it is currently not possible to draw definitive conclusions on the diagnostic performance of electronic noses in the detection of cancer. Adequately powered, multicenter, external validation studies are needed to establish the potential of e-noses in the diagnostic workup of cancer.
Healio: Do you think electronic noses will play a role in the future of cancer diagnosis?
Al-Difaie: Unfortunately, due to the abovementioned shortcomings in the current literature, it is not yet possible to draw definitive conclusions on the diagnostic performance of electronic noses. Therefore, it is currently difficult to determine the potential role of electronic noses in the future of cancer diagnosis. Before clinical implementation can ever be realized, the lack of standardization and reproducibility in the field of e-nose research must be addressed first.
Healio: What future research do you have planned in this area?
Scheepers: We are conducting a prospective proof-of-concept study for the diagnosis of differentiated thyroid cancer in exhaled breath, blood and urine via VOC detection using gas chromatography-ion mobility spectroscopy (GC-IMS) techniques. We hope that this study will help us to get more insight into the specific VOCs in patients with differentiated thyroid cancer. Furthermore, we hope that this study will help us further elucidate the appropriate steps to combat the lack of standardization and reproducibility in the field of e-nose (breath) research.
For more information:
Max Scheepers, MD, and Zaid Al-Difaie, PhD, can be reached at Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, the Netherlands; email Scheepers at m.scheepers@maastrictuniversity.nl.
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