Breath test helps identify colorectal cancer
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A non-invasive breath test that measures exhaled volatile organic compounds may help in the diagnosis of colorectal cancer and advanced adenomas, according to results of a multicenter study.
Kelly E. van Keulen, of the department of gastroenterology and hepatology at Radboud University Medical Center, and colleagues wrote that analyzing volatile organic compounds (VOCs) is a newer technique in the world of colorectal cancer but is already showing some promise.
“Some potential CRC-associated VOCs have already been identified in small pilot studies, but the VOCs identified differed among studies and (external) validation of the results is lacking,” they wrote. “Data on VOCs associated with colorectal polyps is even more scarce.”
Researchers conducted a multicenter study comprising 511 adults scheduled to undergo a colonoscopy. Patients also submitted breath tests using Aeonose devices (The eNose Company). Researchers randomly assigned two-thirds of the breath tests to develop training models, which they used to predict the diagnosis of the remaining patients.
Investigators excluded 64 patients from their analysis due to inadequate breath tests, incomplete colonoscopy or colitis, and grouped the remaining results based on the most advanced lesion found during colonoscopy; CRC (n = 70), advanced adenoma (n = 117), non-advanced adenoma (n = 117), hyperplastic polyp (n =15) and normal colonoscopy (n = 125).
The training models for CRC and advanced adenomas had an area under the curve of 0.76 and 0.71, respectively, and blind validation returned AUCs of 0.74 and 0.61. The final model for CRC had an AUC of 0.84 (95% sensitivity, 64% specificity), while the final advanced adenoma model had an AUC for 0.73 (79% sensitivity, 59% specificity).
“Future studies in the field of VOC analysis should focus on standardizing all phases of VOC analysis among different gas analysis techniques to obtain a translatable approach for future VOC research,” van Keulen and colleagues wrote. “Large scale studies are required to evaluate the influence of covariates on VOC profiles (eg, co-morbidities, medication use, lifestyle factors) and to explore the full diagnostic potential of VOC analysis, preferably with external validation.” – by Alex Young
Disclosure: The authors report no relevant financial disclosures.
Perspective
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The goal of colon cancer screening is to identify either pre- or early stage cancers. We have invasive and noninvasive screening tests. Many of the noninvasive tests are stool based, and look for components of blood or DNA. We know that colon cancer screening works, but only about two-thirds of the population is up to date. Each test has its pros and cons, so we’re always looking for new ways to improve screening adherence.
This study is unique because it looks at a different noninvasive way to identify cancer or precancer and that is through volatile organic compounds found in breath. It’s essentially a proof-of-concept study and demonstrates that this technique, once refined, can add to the armamentarium of colon cancer screening tests with the ultimate goal of improving adherence. However, I don’t think it is fair to look at the sensitivities and specificities yet, because a lot of the process has to be refined, standardized and validated before we can comment on how well it performs.
We’re unaware of what volatile organic compounds we are looking at. In this study, the researchers used artificial intelligence to correlate patterns of volatile organic compounds found in breath with colonic findings. There are many steps in the process that have to be determined, standardized, and validated. Some examples include how the organic compounds are measured (which compounds, at what levels, or a signature pattern), when and how they should be collected, how the samples are stored and processed, whether the process can be replicated, and how frequently the test should be done.
While this is a novel idea, it is not ready for primetime yet. The authors referenced previous research that evaluated the use of volatile organic compounds for detecting other cancers which haven’t proven to be effective, so it’s still too early to tell how this is going to pan out.
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