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Can dogs smell cancer?

Original Publication Date: January 4, 2016
By C. Sue Furman, Ph.D.

News reports often feature dogs trained to detect drugs, explosives and lost, injured or deceased people by smell.

Recent research demonstrates dogs can sniff a person and determine if he or she has cancer.

Both human and dog noses have scent receptor cells that recognize odor molecules by their shape and send nerve signals to the brain for analysis. The 5 million scent receptor cells of a human nose are no match for the many millions of scent receptors a dog's nose possesses.

You can smell a spritz of perfume in a room. A dog can detect the same spritz of perfume in an enclosed stadium and distinguish the ingredients.

It is not surprising that a dog can identify distinctive molecules emitted in the breath of cancer patients.

Dogs are trained to smell cancer the same way dogs are trained to detect explosives and drugs. They are given a high-value reward when the target odor is recognized. The scent that distinguishes gun powder or narcotics can be isolated. The cancer scent may be one of thousands of organic compounds within a human breath. Somehow a dog can sort through the many molecules and determine if a cancer scent is present.

Pine Street Foundation's Michael McCulloch and coworkers recently used a food-based reward system to train five ordinary household dogs with only basic behavioral puppy training skills to sniff for cancer. In a matter of weeks, the dogs were taught to distinguish by scent the breath samples of 55 lung and 31 breast cancer patients from those of 83 healthy people. Sitting or lying in front of a cancer sample got the dog a food reward. Ignoring a non-cancer sample was a correct response.

Once trained, the dogs' sniff detection was tested using breath samples from subjects they had not encountered during their schooling.

The dogs identified the breath of lung and breast cancer patients and healthy people with a high degree of accuracy. Their results were confirmed by conventional biopsy diagnoses.

A dog's nose can sniff out drugs, bombs, and cancer! A dog's nose can sniff out drugs, bombs, and cancer!
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It is remarkable their sniff sensitivity for both cancers was as accurate for people with Stage 1 cancer as for those with Stage 4 tumors.

Other studies confirm canines have the ability to identify people with lung and breast cancer.

Research concerning the types of cancers dogs can efficiently identify is in its infancy. Reports indicate dogs can identify many types of cancer, including human ovarian cancer, melanoma, colorectal cancer and bladder cancer.

Dogs that detect drugs and explosives are essential assets. Whether sniffer dogs will become valuable for diagnostic evaluation remains to be seen. It is promising that canines are able to detect cancers in very early stages, often before they can otherwise be diagnosed.

Perhaps someday, diagnostic sniffer dogs will be prescribed along with X-rays and MRIs.

Sue Furman, Ph.D, has published two books and a DVD on canine massage and teaches classes in pet massage, acupressure, first aid and CPR. See her schedule and submit questions at