How Do Dogs Smell Cancer?

Over the past decade organisations such as the InSitu Foundation have been harnessing the noses of our canine friends to smell out cancer in its earliest forms. Since there are not screening methods to detect all types of cancer at its earliest stages — the speed at which dogs are able to detect cancerous cells could be of invaluable use in identifying cancer early on; giving the patient the best chance of survival.

But how exactly do the dogs do it? They can’t simply be smelling the disease itself, can they?

The power of the canine nose

Whilst dogs don’t actually smell cancer itself — they can detect its tell-tale marker signs. Like many other illnesses, cancer alters a cell’s metabolic state and the metabolites generated by the affected cell. Generally speaking, cancerous cells are metabolically more active than healthy ones — which can manifest itself in the production of different and excessive volatile organic compounds (VOCs).

By sniffing samples of human faeces, skin, blood, sweat, urine or exhaled breath, the super sensitive nose of man’s best friend is able to differentiate between specimens with high numbers of VOCs and those without. As such, they can be quicker and cheaper at effectively detecting cancerous cells than existing tests — and perhaps more importantly — they can detect cancerous cells early in the developmental stage giving the best prognosis for the patient.

In fact, the dogs can even be trained to determine the presence of specific types of cancer, including colon cancer, breast cancer and prostate cancer. As a result, the humble pooch is a powerful tool in fighting off cancer in early-sufferers.

Chromatography or canine

It is possible to detect VOCs in human samples without the use of dogs — thanks to techniques such as thermal desorption gas chromatography with mass spectrometry (TDGC-MS). This process breaks down a compound into its various components and is able to identify individual VOCs which will vary depending upon the type of cancer the patient has.

For a greater understanding of such methods and how they relate to the detection of cancer, other diseases and health issues on the whole, check out the article, Volatile Organic Compound Determination in Health-Related Research: A Review.

However, we have not quite mastered the science behind such detection, as yet. With such a wide variety of VOCs relating to different forms of cancer — it has not yet been possible to accurately identify all of them in the most recent studies. Though most success rates were above 80% — the lowest success rate fell to a mere 59%.

By contrast, the nose of the canine can be far more accurate. Indeed, when it comes to colorectal cancer, the dogs can outperform the technology — with the dogs delivering results of 97% sensitivity and 99% specificity.

Clearly, man’s best friend has proved their value yet again, and though the time, effort and expense invested in training dogs to sniff out cancer is significant, the rewards are undoubtedly worth it.