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Volatile organic compounds in exhaled breath may identify colorectal cancer
Analysis of exhaled volatile organic compounds may be a useful screening tool for colorectal cancer, according to recent results.
In a prospective, two-phase observational study, researchers collected about 2 liters of exhaled breath from each of 37 patients with colorectal cancer and 41 matched controls in an inert Tedlar bag. Contents were then evaluated using thermal-desorber gas chromatography–mass spectrometry to determine the presence of volatile organic compounds (VOC). In a subsequent validation phase, VOCs that could serve to discriminate between patients and controls were tested on 15 additional patients with colorectal cancer and 10 controls, and a probabilistic neural network (PNN) was used to determine the VOC pattern best able to discern patients from controls.
During the trial phase, 58 VOCs were detected, with no single compound serving as an absolute marker. After excluding infrequently observed and background VOC concentrations, 15 potentially discriminating VOCs were evaluated as a pattern, with recognition capabilities ranging from 59% (4-methylundecane) to 96% (1,3-Dimethylbenzene). Investigators observed no significant differences in VOC patterns according to cancer stage or sex.
The application of a PNN model to this pattern resulted in an 86% sensitivity, 83% specificity and 85% accuracy, with a calculated AUROC of 0.852. During the validation phase, the VOC pattern accurately classified 19 of 25 patients as patients with colorectal cancer or controls, for an accuracy of 76%.
“The availability of an effective and reliable colorectal cancer screening tool is of paramount importance in the health service plans of Western countries to permit early diagnosis and/or identification of precursor polyps,” the researchers wrote. “The present findings further support the value of breath testing as a screening tool. The next step will be to increase the number of [patients] involved in order to make this evaluation easier, to identify a diagnostic marker and to improve the performance of the statistical method when applied to samples in a blinded fashion.”