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Canine Cancer Detector: The Poop Pooch

June 21, 2012

Eva Gusnowski

Colon cancer is pretty common, more so than many people would want to believe. The best screening method so far is a colonoscopy, where a flexible camera is used to visualize the inside of the colon. Many people are apprehensive to get this test, and of course, the worst screening method is the one that doesn’t get done. So a recent study has looked at alternatives to this test…using dogs.

 



Now, you know from a previous Science in Seconds entry that the giant African rat has been used to smell tuberculosis in sputum samples, which in and of itself is pretty darn amazing. And in 2011 a group in Japan has done similar training with a black Labrador retriever. Only this time, the dog has been trained to detect colon cancer in patients by smelling their feces and their breath. Cancer smelling dogs aren’t actually smelling the cancer cells themselves, because how would you expect them to detect cancer cells from colon cancer in breath samples? This is possible because early on in the development of the cancer, the cells release volatile organic compounds that can be expelled in the breath. These compounds are what the dogs can detect as a “positive” sample.

 



The canine wonder, Marine, used in this study was no ordinary dog to begin with. She was trained as a water rescue dog for 2 years, and then switched to cancer detection in 2005. By the time this study began, this lab was already able to detect oesophageal cancer, breast cancer, lung cancer, gastric cancer, pancreatic cancer, hepatocellular carcinoma, cholangiocarcinoma, colorectal cancer, prostate cancer, uterine cancer, ovarian cancer and bladder cancer in breath samples. (Oh, is that all?  And during the training, her reward was a tennis ball for correctly identifying the cancer sample among the controls. A tennis ball! If only we were all so easily pleased.) So they decided to try her hand (paw?) at colon cancer in stool samples.

What’s pretty amazing is that Marine was able to identify colon cancer correctly in 97% of the known cases, and was able to correctly identify those without colon cancer 99% of the time (the sensitivity and specificity, which I miraculously learned this year in school despite its statistical nature). These numbers were even better than with the breath tests, which she was initially trained in. Remarkably, Marine was even better for early stage colon cancer detection, which is the best time to catch colon cancer because it is the easiest to treat.

 

marine, science in seconds, cancer sniffing dog

The researchers even tried to trip her up by presenting stool samples with non-colon cancer conditions: bleeding or inflammatory colorectal disease, including ischaemic colitis, non-peculiar colitis or ulcer, ulcerative colitis, diverticular bleeding, mesenteric panniculitis and chronic appendicitis. But these didn’t slow up the poop pooch, she knew they weren’t what she was looking for.

Although this story is pretty amazing, the time required to train and educate the dogs is currently too long and the training is much too expensive to make it feasible on a large scale. So in the meantime, make sure to go for regular screening and talk to your physician about when a colonoscopy is right for you.

Dogs: they smell your shit and work for balls. No wonder they are man’s best friend.

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