Liz Meszaros, MDLinx | July 12, 2019
Cancer-sniffing dogs may be the key to earlier detection of lung and other cancers, according to a recent study published in The Journal of the American Osteopathic Association.
The idea that dogs can sniff out or somehow sense diseases is not a new one. Because they can have up to 300 million olfactory receptors in their noses-- compared with only about 6 million in the average person-- dogs naturally have a much more powerful sense of smell.
And, researchers have verified that some illnesses can significantly change a person’s odor, as can the chemosignals emitted by the body as a manifestation of human emotions. Dogs—with their superior sense of smell--can detect and possibly decipher these changes.
Indeed, it’s been shown that dogs have the ability to accurately detect malaria, Parkinson’s disease, and diabetes, as well as certain types of cancer. For example, researchers demonstrated that giant schnauzers could detect ovarian cancer in blood serum samples with 100% sensitivity and 97.5% specificity. Seizure-alert dogs are yet another example of the usefulness of dogs’ olfactory senses in detecting disease.
In this pilot study, researchers set out to assess the accuracy of the sense of smell of dogs in differentiating the smell of blood from patients with lung cancer.
To do so, they chose to use beagles due to their superior olfactory abilities, small size, calm and highly sociable natures, as well as their high trainability. Beagles, in fact, are known as scent hounds—dogs that hunt primarily using scent rather than sight. Renowned for their superlative sense of smell, scent hounds include beagles, bassets, bloodhounds, and German pointers.
Researchers also chose to do this double-blind study using non-small cell lung cancer because it is more common than small-cell lung cancer, and easier to treat after early detection.
Over the course of 8 weeks, three 2-year old beagles were trained to use scent to distinguish blood serum from patients with newly diagnosed lung cancer from blood serum from 10 healthy controls (6 women, 4 men). The dogs were trained to sit down for a positive cancer finding or to move on when they detected nothing.
When led into a room where the serum samples were positioned at nose level, the trained dogs correctly identified cancer serum samples with a sensitivity of 96.7%, a specificity of 97.5%, a positive predictive value of 90.6%, and a negative predictive value of 99.2%.
“Right now, it appears dogs have a better natural ability to screen for cancer than our most advanced technology,” said coauthor Thomas Quinn, DO, professor, Lake Erie College of Osteopathic Medicine, Erie, PA. “Once we figure out what they know and how, we may be able to catch up.”
In a previous study, researchers documented the ability of dogs to detect lung cancer in breath samples. The current pilot study is the first to test dogs’ abilities in sniffing out lung cancer in serum samples.
In a second phase of the study that is currently underway, the dogs are working on identifying lung, breast, and colorectal cancer using breath samples from subjects. So far, noted the researchers, the dogs seem to be as effective in detecting the presence of cancer using these samples as they were using serum samples.
According to Dr. Quinn, the long-term goal is to develop an over-the-counter screening test, similar to a pregnancy test, that anyone can breathe into and see a color change that indicates a positive or negative cancer finding.
He and his colleagues are enthusiastic about these results, and hope that they have provided a basis for larger studies to assess the use of canine scent detection as a screening tool for lung cancer—currently the leading cause of cancers deaths worldwide, as well as other cancers.
“We’re using the dogs to sort through the layers of scent until we identify the tell-tale biomarkers. There is still a great deal of work ahead, but we’re making good progress,” he concluded.