Can Dogs Sniff Out Cancer?

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Paula Bockman-Chato of Australia has a four-legged furry friend to thank for saving her life. Her dog, Kaspar, became focused on a spot under his owner’s arm which was later detected as early-stage lymph node cancer. Over the past few years, studies have found that dogs are highly successful in sniffing out cancer, and possibly other conditions, in humans due to their highly sensitive sense of smell.

According to James Walker, director of the Sensory Research Institute at Florida State University, a dog’s sense of smell is about 10,000 to 100,000 times superior to that of humans. His research from 2004 found that dogs could sniff out melanomas.

Dr. Sheila Segurson, a veterinarian at the UC Davis School of Veterinary Medicine, says “"It's something where there is no validated research behind it, but at the same time it makes sense. When someone has cancer, the person is metabolically different. Theoretically, dogs would be able to smell that in the same way they can detect when someone is about to have a seizure. They're detecting metabolic changes."

Diseases give off odors that are imperceptible to human noses. For example, people with diabetes often give off fruity smells, due to ketones. Liver disease is associated with a musty smell. Cancer cells emit different metabolic waste products than normal cells. These differences can be detected by a dog’s keen sense of smell, even in the early stages.

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In the journal Integrated Cancer Therapies, researchers from the Pine Street Foundation in California trained five dogs to identify breath samples from people with and without either lung cancer or breast cancer, which are known to exhale patterns of biochemical markers. The dogs had a high rate of success, identifying 55 lung and 31 breast cancer patients.

In Britain, researchers published a study in the leading medical journal BMJ that found that dogs can be trained to recognize and flag bladder cancer. In the study, six dogs had to distinguish one cancerous urine sample from six non-cancerous samples. The dogs found the positive result 41% of the time. While this may seem small, it is significant because it meant that the dogs actually smelled the cancer, and not just guessing.

In the research, there is not a particular breed of dog that is more successful. The studies have involved Labrador retrievers, schnauzers, poodles, and cocker spaniels. All dogs have the same number of olfactory cells in the nose, however not all dogs are motivated by their sense of smell. The dogs used in research have been trained to detect the particular smells associated with cancer much the same as bomb-sniffing dogs are trained.

Researchers at the Pine Street Foundation hope to expand their research to detect early-stage ovarian cancer and pancreatic cancers, which are often diagnosed at a late and less treatable stage. Scientists from Cambridge are working on a study with dogs detecting prostate cancer.

Bockman-Chato is one that hopes the research is ongoing. She has been cleared by her doctors after her diagnosis, and thanks Kaspar for saving her life.

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