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Can dogs smell cancer?
Source: (cancerfacts.com)
Friday, January 13, 2006
SAN ANSELMO, Calif. – Jan. 13, 2006 – Dogs can accurately identify cancer from breath samples of people with lung and breast cancer according to a new study, giving new meaning to the term, "sending a sample to the lab."
In a new scientific study, led by Michael McCulloch of the Pine Street Foundation in San Anselmo, Calif., and Dr. Tadeusz Jezierski of the Polish Academy of Sciences, Institute of Genetics and Animal Breeding, researchers show in a controlled study that dogs' acute sense of smell can distinguish people with both early and late stage lung and breast cancers from healthy people.
"Training was efficient and cancer identification was accurate," the authors wrote. "In a matter of weeks, ordinary household dogs with only basic behavioral "puppy training" were trained to accurately distinguish breath samples of lung and breast cancer patients from those of controls.
The researchers add that identification of the chemical elements of the breath samples could lead to development of new tests for cancer. The study will appear in the March 2006 issue of the journal Integrative Cancer Therapies.
In the study, researchers trained, within a three-week period, five household dogs, three Labrador retrievers and two Portuguese water dogs aged seven years to 18 months, to detect lung or breast cancer by sniffing the breath of cancer patients, who did not participate in the study.
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, humane methods of dog training employing food rewards and a clicker, as well as assessment of the dog's behavior by observers blinded to the identity of the cancer patient and control samples were used in the training.
Once the dogs were trained, the researchers recruited two groups of study participants. One group included 86 cancer patients (55 with lung cancer and 31 with breast cancer) and the other control, or comparison group, included 83 healthy patients without cancer.
All cancer patients had recently been diagnosed with cancer through biopsy-confirmed conventional methods such as a mammogram, or CAT scan and had not yet undergone any chemotherapy treatment. During the study, the dogs were presented with breath samples from the cancer patients and the controls captured in special individual tubes.
The results of the study showed that dogs can accurately detect breast and lung cancer between 88 percent and 97 percent of the time. 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, once further work has been carried out to standardize and expand this breath sample method of detection.
Other scientific studies have documented the abilities of dogs to identify chemicals that are diluted as low as parts per trillion. The clinical implications of canine olfaction first came to light in the case report of a dog alerting its owner to the presence of a melanoma by constantly sniffing the skin lesion.
Subsequent studies published in major medical journals confirmed the ability of trained dogs to detect both melanomas and bladder cancers. This new study is the first to test whether dogs can detect cancers only by sniffing the exhaled breath of cancer patients.
The researchers hope to conduct a larger study to closely examine the chemistry of exhaled breath to identify which chemical compounds can most accurately identify the presence of cancer and to compare both biological (canine scent detection) and chemical methods of detecting those chemical compounds.
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