In Europe, it affects 20 to 35 persons per 100,000 inhabitants. Each year, 33,000 new cases are detected in France, with more than 16,000 deaths caused yearly. The problem with this type is cancer is that symptoms may not appear until it is too late, when generalized metastasis is already present. CRC, when treated at an early stage, is relatively innocuous; for this reason it is crucial to be able to detect it at an early stage. At present, two screening tests have been developed—colonoscopy, which is an invasive technique, and the search for blood in stools. Unfortunately, the latter only detects relatively advanced stages of the disease.

Based on work already undertaken in lung, breast and prostate cancers, a Japanese study focused on scented particles as markers of CRC. In order to detect these odorous particles in exhaled breath samples and in stools, the authors trained a Labrador dog who sat down each time it scented the sample of a patient with CRC. For this study, the authors made the dog sniff a series of 5 boxes containing exhaled breath or stools. Among the 36 samples of exhaled breath from patients at different stages of CRC, only 3 were not detected by the dog. Even more impressive, in the 37 samples of stools from patients with CRC, only 1 was not detected by the dog. The animal was much more efficient than the existing test for detection of stool samples, which could only detect 11 CRCs out of 37. Moreover, in terms of different stages of the disease, the dog was able to detect even very early stages of CRC.

Apart from the originality of this study, the authors showed that there exist odor materials specific to CRC whatever the stage of the disease. Such scented particles can be detected in stool samples, which are easily obtainable. At the present time, machines capable of detecting such odor materials exist, but the nature of the particles remains to be determined.

Par Laurent Dubuquoy

References

Sonoda H, Kohnoe S, Yamazato T, Satoh Y, Morizono G, Shikata K, Morita M, Watanabe A, Morita M, Kakeji Y, Inoue F, Maehara Y. Colorectal cancer screening with odour material by canine scent detection. Gut 2011 Jun;60(6):814-9. Epub 2011 Jan 31.