Breath Test for Colon Cancer Shows Promise

Breath Test for Colon Cancer Shows Promise

Douglas K. Rex, MD, MASGE, reviewing Woodfield G, et al. Gastroenterology 2022 Jul 5.

Patients with certain cancers expel volatile organic compounds (VOCs). VOCs are the basis of previous reports in which dogs were trained to identify patients with cancer from their breath. 

In this trial, patients enriched with colorectal neoplasia underwent a breath test based on gas chromatography-mass spectrometry identification of various VOCs. A multivariate model based on VOCs and clinical metadata was developed. 

Of 1432 included patients, 357 had a normal colonoscopy, 188 had benign disease including hemorrhoids or diverticular disease, 106 had inflammatory bowel disease, 348 had low-risk polyps, 67 had intermediate-risk polyps, and 204 had high-risk polyps. In addition, 162 patients had colorectal cancer (CRC), 64.2% of which were T3 or T4 cancer. 

A diagnostic model based on 14 VOCs and body mass index predicted CRC with an area under the receiver operating characteristic (AUROC) curve of 0.87, sensitivity of 79%, specificity of 86%, and negative predictive value (NPV) of 97%. In patients with symptoms, the model had an AUROC curve of 0.91, sensitivity of 83%, specificity of 88%, and NPV of 96%. Polyps of any risk category could be predicted with an AUROC curve of 0.67, sensitivity of 66%, and specificity of 58%, compared with patients with no polyps or cancer and based on 16 endogenous VOCs and age. A model based on high-risk polyps did not perform better.

Douglas K. Rex, MD, FASGE


These data indicate that breath testing might be a useful adjunct for CRC screening, though it is not yet of value for polyp screening. Some performance features may be worse in a true screening population.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.


Woodfield G, Belluomo I, Laponogov I, et al. Diagnostic performance of a non-invasive breath test for colorectal cancer: COBRA1 study. Gastroenterology 2022 Jul 5. (Epub ahead of print) (

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