Dogs may help detect cancer of the colon

By Deborah Kotz
Globe Staff / February 2, 2011

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Who says you can’t teach an old dog new tricks? Japanese researchers say they’ve successfully trained an 8-year-old female black Labrador retriever to sniff out colon cancer on the breath of a patient.

Published Monday by the digestive health journal Gut, the study adds to previous research suggesting that dogs can be useful for cancer detection. Studies over the past few years have shown that dogs can detect melanoma, bladder, lung, ovarian, and breast cancer, also by sniffing the breath of cancer patients.

Their amazing sense of smell allows dogs to identify chemicals that are diluted as low as a few parts per trillion. It’s why we rely on man’s best friend to sniff out bombs and drugs at airports.

In the current study, the black Lab sniffed 33 breath samples from patients with colon cancer and 132 samples from healthy controls, about half of whom had benign colon polyps. The dog sniffed each sample, five to a group, and was trained to sit in front of the one that had cancer.

She correctly identified those who had cancer 91 percent of the time — correctly distinguishing between cancerous and benign polyps — and was correct in excluding healthy samples 99 percent of the time when compared with findings on a colonoscopy.

When the dog was given watery stool samples to sniff instead, she was able to find 97 percent of the cancers with the same specificity rate of 99 percent. The fecal occult blood test, another routine colon cancer screening method that checks for blood in the stool, detected about 70 percent of the cancers and had a specificity rate of 85 percent.

If you’re looking to get out of a colonoscopy, however, no such luck — at least for a while. The dog-sniffing method is hardly ready for prime time, given the small amount of samples that have been tested.

There’s also the matter of training the dogs. “It may be difficult to introduce canine scent judgment into clinical practice,’’ write the study authors, led by Dr. Hideto Sonoda of Kyushu University at Fukuoka, “owing to the expense and time required for the dog trainer and for dog education.’’

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