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Lab test shows dogs can diagnosis colon cancer

Kathleen Blanchard's picture
Colon cancer

A specially trained Labrador retriever was able to accurately diagnose colon cancer from breath and stool samples in a new study. Scientists say that new colon cancer diagnostic tests could be developed based on the finding. In tests, the dog was able to find colon cancer with 98 percent accuracy, compared to colonoscopy, with a 95 percent overall accuracy rate.

In a study, the dog was presented with 74 separate sniff tests over a period of several months from breath and stool samples. Just one of the samples was from a patient with cancer each time.

Included were 48 patients with known bowel cancer and 258 volunteers with no history or current diagnosis of cancer. The samples that came from cancer patients were in early and late stages. In breath and stool samples, the dog accurately identified which were cancerous, in all but one instance.

The Labrador identified cancer in 33 out of 36 breath tests and in 37 out of 38 stool tests. Some of the patients had polyps and other had inflammatory gut problems that the researchers suspected might interfere, but instead posed no problem for the dog.

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The findings, according to the researchers, means cancer cells give off odors that circulate in the body. Rather than use dogs to sniff out cancer, the scientists say a sensor could be developed to detect the disease in early stages when cancer is most treatable.

The authors note "Early detection and early treatment are critical for the successful treatment of cancer and are excellent means for reducing both the economic burden and mortality [of bowel cancer]," comment the authors.

They also note anecdotal evidence showing dogs can identify other types of cancer. In the March 2006 issue of the journal Integrative Cancer Therapies, trained dogs were able to identify breast and lung cancer by sniffing breath. The study, "Diagnostic Accuracy of Canine Scent Detection in Early and Late Stage Lung and Breast Cancers" suggested breath analysis could be used as an adjunct for more accurate cancer diagnosis. Dogs have also been shown to able to detect melanoma.

A 2004 study showed dogs could also detect bladder cancer. The study, published in the British Medical Journal used six dogs who were given urine samples from patients with and without cancer. The authors concluded "dogs can be trained to distinguish patients with bladder cancer on the basis of urine odour more successfully than would be expected by chance alone", in the study titled "Olfactory detection of human bladder cancer by dogs: proof of principle study."

The dog used in the current study was able to detect colon cancer in 95 percent of the samples, even in patients with conditions like ulcers, inflammatory bowel disease, colon polyps , diverticulitis and appendicitis. The researchers hope to develop technology that can "sniff out" cancer, given the impracticality of using dogs to do the job.

Gut doi:10.1136/gut.2010.218305
"Colorectal cancer screening with odour material by canine scent detection"