Man’s Best Friend? Dogs Can Detect Colon Cancer, Research Says

Colon Cancer Sniffing DogColorectal cancer caused more than 665,000 deaths worldwide last year. This cancer is fourth on the list of cancer diagnoses in the United States, and in the West, it is the third leading cause of deaths attributable to cancer complications. Since colorectal cancer is difficult to test in its early stages, most victims of the disease do not know they have it until it has progressed to a much more serious phase. The current standard fecal occult test used to detect colorectal cancer has a low success rate in early-stage cancer, and even subsequent colonoscopy exams are not 100% accurate. Considering this fact, a test that could not only detect cancer early but also in a non-invasive fashion would be something the world would receive gladly.

Who knew that a dog would prove itself “man’s best friend” in yet another—and very astonishing—way?

Researchers at the Kyushu University in Japan released the findings of a study they recently concluded in Britain’s Gut magazine, a medical journal, and those findings were intriguing. According to the study, dogs can detect colon cancer from breath and fecal samples at a rate better than 9 out of 10 cases on average. The subject pool was more than 300 individuals, 48 of whom had colorectal cancer; and the dog was an 8-year old Labrador retriever named Marine. When Marine was presented with breath samples to sniff, she accurately identified the cancer subjects 95% of the time; when presented with a stool sample, she was right 98% of the time. The study was also published online in the British Medical Journal and has been widely hailed as an excellent step forward in the battle against this deadly cancer.

Researchers don’t know exactly what it is that triggered the dog’s reaction, but it seems that cancer gives off a particular volatile chemical compound (a scent) which is detectable to the extremely sensitive canine nose. A dog’s nose is over a thousand times more sensitive than that of humans, with over 220 million olfactory sensors capable of detecting scent particles in single parts per billion. Already used to sniff out explosives, drugs and other things, dogs have been proven to be able to identify other cancers as well as oncoming epileptic seizures by previous studies, so colorectal cancer identification is not an unrealistic extrapolation of canine abilities. Although using dogs to routinely diagnose cancer would present some practical difficulties (the training and care of such animals is expensive), scientists are challenged to determine what it is that the dogs are detecting, because it may be possible to devise a method of testing for these volatile cancer compounds.  The fecal occult test that is done now to detect colon cancer checks for visible flecks of blood in stool samples, but it has a 20% or less rate of positively detecting early-stage cancers. If the test is positive or inconclusive, it is followed by a colonoscopy—an invasive procedure that most people would rather avoid if possible. A test designed using the knowledge gleaned from analyzing the canine responses would be extremely beneficial.

Further research into this subject is continuing, with more important breakthroughs anticipated as scientists learn more about what dogs can actually teach them.

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