Can Dogs Detect Cancer?

K9 Control UK Dog Trainers

More and more stories are emerging of pet dogs playing a part in the early detection of cancer by literally sniffing out the disease on their owner’s bodies.

This is remarkable in its self, but even more remarkable, is that dogs are detecting these cancers when they are in the very earliest stages, way before any symptoms are present and thus saving lives.

Is it medically proven?

Whilst this may sound a little ‘new age’ the evidence speaks for itself, with scientists now seriously considering the concept and carrying out studies which have unearthed some staggering finds.

For example, in 2010, Japanese researchers showed that dogs can detect cancer from a breath sample, while in 2012, the European Respitorary Journal published a report that found dogs could identify lung cancer in breath samples.

Another study carried out in 2004 by animal behaviorist Dr Claire Guest, became very personal to her five years later when one of her own dogs detected her cancer.

Claire was already convinced that dogs could sense abnormal cancer cells through smells emitted by urine, the skin or even the breath. She carried out a clinical study published in 2004 showing that it was possible to train dogs to detect cancers from samples supplied by patients. The report showed that her dogs correctly identified bladder cancer in 22 out of 54 cases. (The success rate now is 93 percent!). Her findings were not however, always met with enthusiasm, and were dismissed by some of the medical profession.

They had to eat their words however when Claire’s findings saved her own life when one evening in 2009, her Labrador, Daisy, refused to follow her other two dogs out of the car for their evening walk. Instead, Daisy started pawing at Claire’s chest and bumping against her repeatedly. When Claire tried to push her away, she came back again, clearly upset and acting out of character. Over the next few days, Claire detected a tiny lump in the area that had interested Daisy so much. Claire immediately visited the doctor who booked her in for a mammogram.

The lump turned out to be a harmless cyst, however further in the breast tissue was a deep-seated cancer. It was in its very early stages and Claire underwent a lumpectomy as well as having some lymph nodes removed and six months of radiotherapy. Chillingly, Claire was told that by the time the lump would had become noticeable, the cancer would already have spread and the prognosis could have been very different.

Five years and several trials later, Daisy has sniffed 6,000 samples of urine, detecting more than 551 cases of cancer with an impressive diagnostic accuracy of 93 per cent!

Claire’s Charity ‘Medical Detection Dogs’ now has 12 dogs working with the charity to detect traces of cancer from urine and breath samples.

They are also conducting a trial with Buckinghamshire NHS Trust and Milton Keynes Hospital NHS Foundation Trust with samples from thousands of patients. The aim is to glean as much evidence as possible so that eventually dogs can be used as part of the cancer screening process to back up the results of clinical tests.

What makes dogs interested in sniffing cancer?

Dogs can smell in parts per trillion. To illustrate this, if one cc (less than a drop) of blood was diluted into 20 Olympic sized swimming pools, a dog would smell with ease that there is blood in the pool.

To put it into another perspective; humans have five million sensor receptors dedicated to smell compared to dogs who have 300 million. So these dogs are reacting to the smell of cancer.

How using cancer detecting dogs can save the Health Service money

Pro Vice Chancellor of the University of Buckingham, Professor David Billington, who specialises in researching treatments for cancer and diabetes, is a firm believer in the skills of these dogs. ‘The dogs can detect cancer in the urine of patients with prostate cancer more reliably than the PSA test’, he says, referring to the blood test typically used to detect levels of prostate specific antigen, a protein linked to the disease.

‘A positive PSA test is followed up by a multi-needle biopsy, which is unpleasant and invasive. If medics could use dogs to detect cancer from urine as well as using the standard blood test, they can use both factors to decide who needs to undergo a biopsy. It would save the health service a huge amount of money, spare patients unnecessary procedures and save lives.’

Scientists are now developing electronic systems (e-noses) that mimic the way dogs detect the smell of cancer. Most oncologists will tell you that humans can actually smell cancer in latter stages through the patients breath. If we can smell it at stage 3-4, then a dog would be able to detect the scent much earlier, in stage 0, 1 or 2. However, until the ‘electronic nose is developed, only dogs have the ability to smell cancer in such early stages.

How are the cancer detection dogs trained?

The dogs are trained by sniffing urine samples of people with cancer and rewarded when they single out these samples from other urine from non-cancer sufferers.

With breath, however, it can become far more complicated. The cancer scent is one of the thousands of organic compounds within a humans breath. In order for the dogs to generalise the cancer scent, many samples with the common odour must be used. The dogs are also trained to ignore healthy breath as well as breath with diseases other than cancer. To do this means using countless samples within the dogs training.

It’s so exciting to consider how far this work can go and how many lives can be saved thanks to our canine friends.

The work is funded by the trust and charity donations. If you would like to be involved in fund raising for the charity, please go to: for more information.