Dogs' keen sense of smell might help in the early diagnosis
of cancer, researchers report in the current issue of
Integrative Cancer Therapies. The findings show that trained
ordinary household dogs can detect early-stage lung and
breast cancers by merely sniffing the breath samples of
patients.
"We've seen anecdotal evidence before suggesting that
dogs can smell the presence of certain types of cancer,"
Michael McCulloch, from the Pine Street Foundation in
San Anselmo, California stated, "but until now, nobody
had conducted a thorough study such as this." Researchers
have observed that cancer cells release molecules different
from those of their healthy counterparts, and that might
be perceived by smell by the highly sensitive dog's nose.
For the study, five dogs, three Labrador retrievers and
two Portuguese water dogs, were trained by a professional
instructor to respond differently to exhaled breath samples
of healthy and cancer patients. "The dogs learned to sit
or lie down in front of cancer patient samples and to
ignore control samples through the method of food reward,"
McCulloch explained.
After an extensive, though relatively short, period of
training, the McCulloch and his colleagues tested the
animals' ability to distinguish cancer patients from controls.
The animals were given breath samples from 55 patients
with lung cancer, 31 with breast cancer and 83 healthy
controls who were not included in the original training
sessions. Neither the dogs nor the observers knew the
identity of the samples.
McCulloch's group found that the dogs were able to correctly
distinguish the breath samples of cancer patients from
the those of the control subjects in about 90 percent
of the cases, even after the researchers adjusted the
results to take into account whether the lung cancer patients
were smokers. The dogs were also capable of detecting
early-stage lung and breast cancers.
"These results show that there is hope for early detection,"
McCulloch said. The researchers are planning to conduct
further studies on the breath composition of cancer patients
to possibly design an electronic device that can do the
dogs' job. "I hope people will be interested in pursuing
this research," McCulloch added. "It shows that there
is definitely something out there."
SOURCE: Integrative Cancer Therapies, March 2006.
