Dog Smelling Cancer May Lead to Less Invasive Tests

A dog trained to sniff out colorectal cancer was almost as accurate as a colonoscopy in a study that suggests less invasive tests for the disease may be developed.

The Labrador retriever was at least 95 percent as accurate as colonoscopy when smelling breath samples, and 98 percent correct with stool samples, according to the study, published today in the medical journal Gut. The dog’s sense of smell was especially effective in early-stage cancer, and could discern polyps from malignancies, which colonoscopy can’t.

The results point to the existence of volatile organic compounds that might be the basis for non-invasive, early colorectal cancer diagnostics, wrote the researchers led by Hideto Sonoda of Kyushu University in Japan. Colonoscopies involve inserting a tube with a camera through the rectum, and less invasive fecal blood tests only detect early-stage disease in one out of 10 cases, they wrote.

“Most striking is the ability of the dogs to detect bowel cancer at its earliest stages,” Trevor Lockett, a bowel cancer researcher with the Commonwealth Scientific and Industrial Research Organisation in Australia, said in an e-mail.

Most current non-invasive tests for bowel cancer identify later-stage disease far more efficiently than early-stage, Lockett said.

“Detection of early-stage cancers is the real holy grail in bowel cancer diagnosis because surgery can cure up to 90 percent of patients who present with early-stage disease,” he said.

Sniffing Samples

In the study, the dog sniffed samples from 48 people with confirmed bowel cancer and 258 volunteers who were either healthy or had survived cancer. The dog was asked by his handler to find the one malignant sample in a set of five.

“This study shows that a specific cancer smell does indeed exist,” the researchers said in the study. “These odor materials may become effective tools in screening.”

There were about 102,900 new cases of colon cancer and 39,760 case of rectal cancer in the U.S. last year, and 51,370 patients died from the disease, according to the American Cancer Society.

While dogs have previously been shown to identify skin, bladder, lung, breast and ovarian malignancies, canines are too expensive and too fickle to rely on for routine cancer diagnoses, the researchers said.

Labrador retrievers, originally used in Canada to catch fish and pull in nets, now work as guide dogs for the blind, search-and-rescue animals and narcotics detectors, according to the American Kennel Club’s website. It’s the most popular breed of dog in the U.S., according to the club.

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