With the well-deserved title of best friend to man, dogs can bring numerous benefits to our lives, from encouraging more physical activity to reducing feelings of loneliness.
Dogs are also known for their significantly heightened sense of smell, having around 200 million olfactory cells compared to humans who have around 5 million. While they are often used for the detection of bombs and drugs, there have also been cases where dogs have been able to smell the presence of cancer in people.
Stephanie Herfel, 52, recently thanked her Siberian husky Sierra for correctly detecting her ovarian cancer three times. According to Herfel, the dog sniffed her stomach and showed signs of discomfort by “freaking out and rolling up in a tight ball in the back of a closet.”
The first-ever report of this capability was published back in 1989 when a dog, similar to Sierra, appeared uneasy after sniffing at a lesion on a woman’s thigh. Upon having it examined by a doctor, the woman was diagnosed with malignant melanoma.
You may find many such news stories with a quick internet search. But when this potential exists, what is stopping us from training and involving dogs as a part of the screening process for cancer?
Cancer cells are said to have a specific odor which is not strong enough to be detected by the human nose. But over the years, experiments have placed biological samples before dogs to test if they can correctly pick out the malignant sample.
Even though there have been promising results in the laboratory setting, problems seem to emerge when dogs are tested in a screening-like situation.
When the dog sniffs and correctly singles out the cancer-associated sample, it is given a reward — this is necessary as a form of positive reinforcement. However, in the real world, there is no way of immediately knowing whether the dog has correctly identified cancer in a patient.
“I think this was one main point for why our study failed,” said Klaus Hackner, who studies canine cancer detection at Krems University in Austria. “We were not able to provide positive feedback because neither one knew in the screening situation if the dog was right or not. This was stressful for both the dogs and the handlers.”
Though there are success stories like that of Sierra and her owner, dogs are not machines i.e. they can have their off days and are prone to making mistakes. It defeats the purpose of a screening if the dog misses out on the presence of cancer in a patient or incorrectly “detects” cancer in a healthy person.
“I don’t doubt the social and emotional value of dogs as companions, and as active helpers in many circumstances,” physician Peter Lipson wrote with regard to his 2012 review on the subject. “But beyond this, the evidence is wanting.”