The earlier that cancer is detected, the greater the likelihood of cure. Therefore, cancer researchers are always looking for more sensitive tests that can detect cancer at the earliest possible stage. When I was a cancer research fellow working in the lab, I used an exquisitely sensitive chemical test to identify trace amounts of genetic material from otherwise invisible tumor cells floating in the blood or bone marrow of patients who had previously been diagnosed with cancer, and who were thought to have been cured of their disease. (This test, reverse transcriptase-polymerase chain reaction, or RT-PCR, works by “amplifying” trace amounts of genetic material using a powerful chemical reaction.)
There have been many novel strategies proposed to improve our ability to detect cancer at the earliest possible stages, but few have been more novel than the proposed use of domesticated animals to sniff-out chemicals secreted by cancerous tumors in humans. In an extremely novel cancer detection research study, which appears in the current issue of the journal Gut, a specially trained Labrador retriever was employed to sniff the exhaled breath and stool samples of humans. In this innovative pilot study, this specially trained dog was directed to sniff the exhaled breath and stool samples from patient volunteers with colorectal cancer, and patient volunteers without colorectal cancer (all of these patient volunteers subsequently underwent colonoscopy to confirm the presence or absence of colorectal cancer). The results of this preliminary study are, quite simply, amazing.
When compared to the findings at colonoscopy, the “scent detection” dog was able to correctly identify colorectal cancer patients simply by smelling their breath in more than 90 percent of cases! Even more astonishing, this dog was able to accurately identify patients with colorectal cancer 98 percent of the time by sniffing their stool specimens!
Anyone who has undergone colonoscopy knows that the bowel-purging “prep” on the day before is quite unpleasant. (Colonoscopy, itself, can be rather unpleasant, although most patients are moderately sedated, and many patients will have no subsequent recollection of this scope procedure.) Moreover, colonoscopy is an expensive screening test for colorectal cancer, and like all invasive procedures, colonoscopy is associated with a small risk of complications, including bleeding and bowel perforation. Therefore, it is mind-boggling to me that, based upon the results of this very small clinical research study, a specially-trained dog proved to be virtually as accurate in diagnosing both early and advanced colorectal cancers as the “gold standard” colorectal cancer screening test, colonoscopy, merely by sniffing the breath and stool of human volunteers! (As an aside, it has been estimated that dogs have a sense of smell that is hundreds-of-thousand to millions of times more sensitive than humans.)
Of course, the dramatic findings of this intriguing pilot study will have to be validated by larger studies. That being said, the findings of this study are very exciting, and could revolutionize screening for colorectal cancer, and perhaps other types of cancers as well.
Once again, it appears that dogs have truly earned the title of “Man’s Best Friend!”
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Dr. Wascher is an oncologic surgeon, professor of surgery, cancer researcher, oncology consultant, and a widely published author
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