Can Dogs Smell Cancer?

Lung and breast cancers are the leading causes of cancer deaths worldwide. Obviously, early detection of these cancers is desperately needed.

In a new scientific study, researchers have presented surprising new evidence that dogs may be able to detect early cancers in humans.

The study was published a few years ago in the March 2006 issue of the journal Integrative Cancer Therapies published by SAGE Publications. The article relates how researchers found scientific evidence that a dog’s extraordinary scenting ability can distinguish between healthy people and people with both early and late stage lung and breast cancers. The research was performed in California and documented by the BBC in the United Kingdom.

Past scientific studies have documented the ability of dogs to identify chemicals that are diluted in liquids in extremely low volumes. The first unusual canine scenting observation was noted in the report of a dog that alerted its owner to the presence of a melanoma cancer by constantly sniffing the lesion on its owner’s leg. Subsequent studies published in major medical journals have confirmed the ability of trained dogs to detect both melanomas and bladder cancers.

This study is the first to test whether dogs can detect cancers only by sniffing the exhaled breath of cancer patients.

In the study, five pet dogs were trained over a three week period to detect lung or breast cancer by sniffing the breath of cancer patients. The trial consisted of 86 cancer patients (55 with lung cancer and 31 with breast cancer), and a control sample of 83 healthy patients with no cancers. All the cancer patients had recently been diagnosed with cancer using biopsy-confirmed conventional methods such as a mammogram or CAT scan, and none had yet undergone any chemotherapy treatment.

During the study, the dogs were exposed to breath samples captured in a special tube from the cancer patients as well as the control subjects. The dogs were trained to give a positive identification of a cancer patient by sitting or lying down directly in front of a test station containing a cancer patient sample, while ignoring control samples.

Standard methods of dog training using food rewards and a clicker were used in the experiment. The behavior of each dog was also assessed by observers unaware of which participants were cancer patients or control subjects.

The results of this study showed that dogs are able to detect breast and lung cancer with accuracy between 88% and 97%. The high accuracy persisted even after results were adjusted to take into account whether the lung cancer patients were currently smokers.

The study also confirmed that the trained dogs could even detect the early stages of lung cancer as well as early breast cancer. The researchers concluded that breath analysis has the potential to provide a substantial reduction in the uncertainty currently seen in cancer diagnosis.

We all hope that further studies will be undertaken to standardize and expand the methodology used in these experiments.

The study was supported by the MACH Foundation in Fairfax, California and Guide Dogs for the Blind in San Rafael, California.