Dogs that can sniff out prostate cancer from urine samples have been approved for trial by Britain’s National Health Service (NHS) in the hope that it could show up inaccuracies in the current PSA (prostate specific antigen) test.
It is hoped the trial could eventually lead to an “electronic nose” that is able to detect the cancer to a greater degree of accuracy than the PSA test.
It has long been known that a dog’s remarkable sense of smell can detect minute odours known to be associated with many cancers which are understood to be linked to volatile organic compounds produced by malignant cells.
“Dogs have got this fantastic sense of smell; 300 million sensory receptors, us humans have five million,” said Dr Claire Guest, who co-founded charity Medical Detection Dogs in 2008 to train specialist dogs to detect human diseases.
“These dogs have the ability to screen hundreds of samples in a day; it’s something they find very easy, they enjoy their work.”
“So they’re very, very good at finding minute odours. What we now know is that cancer cells that are dividing differently have different volatile organic compounds – smelly compounds – that are associated with the cells.
“And dogs with their incredible sense of small can find these in things like breath and urine.” she said.
Dr Guest said that the dogs’ ability to sense chemical changes has been known throughout history but overlooked by modern medicine.
“What dogs are doing is actually revisiting a way in which diagnosis has been done centuries ago. It was understood then that different volatiles – or smelly compounds – could be involved with changes in our body and may in fact enable someone to make an accurate diagnosis.
“But this has been very much forgotten. What the dogs are doing is finding the odours from bio-chemical changes in our body and this is opening a new way of diagnosing diseases and conditions in the future.”
Dogs detect cancer in 93 per cent of cases in early trials
Medical Detection Dogs gained approval from Milton Keynes University Hospital for further trials, after initial testing showed trained dogs can detect prostate tumors in urine in 93 per cent of cases.
The charity says dogs undergo training for a period of about six months, after which they can reliably identify urine with traces of cancer cells in it.
At the charity’s facility the dogs do the rounds, sniffing a machine that holds eight urine samples.
When they detect the sample that contains cancer cells, they either stop and sit down by it, bark or lick the bottle to indicate they can smell the cancer.
Dogs are initially rewarded when they detect any urine scent, and then later only rewarded when they successfully identify cancer cells in urine samples.
Dr Guest said dogs can detect the scent of cancer almost instantly, meaning they could potentially check many more samples than a human could possibly do.
“These dogs have the ability to screen hundreds of samples in a day; it’s something they find very easy, they enjoy their work. To them it’s a hunt game – they find the cancer,” she said.
For Dr Guest, it was this ‘game’ that potentially saved her life.
In 2009, her labrador Daisy made her aware that she was suffering from the early stages of breast cancer when she began to nudge Dr Guest’s chest.
Daisy, now age 11, is one of the dogs taking part in the trials in Milton Keynes.
Prostate cancer most common cancer in UK men
According to the charity, there are strong reasons for such a study.
Prostate cancer is the most common cancer in men in the UK, and the second most common cause of cancer death.
The current PSA test involves analysing a blood sample for a specific protein produced by the prostate gland; an elevated level of which could indicate prostate cancer and require a biopsy to be carried out.
But the test has a high ‘false positive’ rate meaning many men may undergo the invasive procedure unnecessarily, and many general practitioners are reluctant to use it.
The scientists hope that dogs could provide a second line cancer screening service that demonstrated a low false positive rate and higher accuracy. And if dogs can be proved to be a reliable screening tool, a test could eventually be developed that is far superior to the PSA test.
“Dogs could be used potentially to look at any other diseases which also had a chemical signature.”
While the current trials are focused on training dogs to accurately detect prostate cancer in urine samples, Rowena Fletcher from Milton Keynes University Hospital says dogs’ unique skill could make them a valuable resource for doctors in detecting many more diseases.
“A lot of different diseases could carry a chemical signature, and then really the dogs could be used potentially to look at any other diseases which also had a chemical signature,” she said.
For now, a viable ‘electronic nose’ is still many years away, with no technology able to get close to the sniffing power of man’s best friend.