On the scent of cancer

Ever since dogs found hunter-gatherers’ campsites a good place to scavenge and decided to adopt humans, we have created roles for them: hunting, protecting property, mountain rescue, companionship, and as ‘assistance dogs’.

No doubt dogs have been helping people with poor vision for millennia, but it was a German doctor looking after soldiers blinded by gas who in 1916 started the first formal training scheme. Fifteen years later two British dog breeders, Rosamund Bond and Muriel Crooke, trained the first four British guide dogs for the blind. Now there are 5000.

It isn’t a great leap to training dogs to assist people with hearing loss – there are 900 deaf dogs partnerships – or with neurological and degenerative diseases, or seriously disabling injuries – Hounds for Heroes provides dogs for ex-servicemen. Dogs can be trained to pick up the TV remote, flush the loo and empty the washing machine. They can retrieve cash from an ATM and help their owner turn over in bed. And they can put their own feeding bowls in the sink and tidy away their own toys. Well ahead of most human teenagers, then.

An assistance dog costs around £50,000 over its working life. Owners have a contract with the charity which supplies their dog, and they contribute what they can to their dogs’ care and vets’ bills. There is no funding from government. Fortunately the public gives generously to the charities which breed, train and register assistance dogs.

Owner and dog have to be compatible, and not just temperamentally. If you are five feet tall, a poodle would be more your stride than an Alsatian. It’s hard work being an assistance dog and they retire early, after about six years, though some stay with their owners as pets.

The owners are in control of their dogs and are responsible for their good behaviour, but a dog needs ‘intelligent disobedience’: if its owner instructs it to lead him down what he thinks is a flight of steps, his dog has to recognise that it is a precipice and refuse to go on.
Under the 2010 Equality Act, registered assistance dogs must be admitted to pubs, cafes and restaurants. Taxi drivers are required to carry guide dogs. Occasionally drivers have tried to refuse, sometimes citing religious prohibitions, though in 2003 the Sharia Council ruled that working dogs are exempt from the proscription on unclean animals.

Airlines too are obliged to provide registered assistance dogs with floor space, normally at no extra charge. In the USA some passengers try to wangle a free place for their pet by waving a doctor’s letter, but airlines require to see a dog’s registration document, so passengers claiming that their pet pooch is an ‘emotional assistance dog’ will find themselves paying for Fido to travel in a crate in the hold.

By the way, if you come across someone out with a guide dog, resist the temptation to stroke it – it’s at work.

You probably wouldn’t be tempted to stroke a sniffer dog, particularly one accompanied by a US marshall. But dogs’ olfactory abilities are also put to medical uses. People with a history of anaphylactic reactions can have a dog trained to detect nuts, or a dog can warn its owner of an oncoming hypo or an Addisonian crisis or a life-threatening cardiac arrhythmia. Sufferers and their families can relax their vigilance and live a more normal life. It’s a shame for people with epilepsy that there is only weak evidence that dogs can be trained to warn of impending seizures.

Researchers are on the scent of more roles for medical detection dogs. A study in the BMJ in 2012 showed that a trained beagle identified Clostridium difficile in stool samples with 100% sensitivity and specificity, and its results were nearly as good when it was taken on the ward to sniff patients. An unorthodox way of overcoming the current delays in diagnosis?

There are many anecdotes of dogs suddenly and repeatedly pawing or nosing their owner’s breast, worrying her to the point that she goes to see her GP and a breast cancer is discovered. Research is now providing evidence that dogs can detect signs of malignancy, at least in vitro. In 2004 the BMJ published a trial which showed that dogs sniffing urine samples did better than chance at identifying the patient with bladder cancer.
What are dogs detecting? It is known that some cancers produce unusual volatile compounds. How specific are these molecules and can they be identified and used for screening? Milton Keynes Hospital and the charity Medical Detection Dogs have permission for a trial of dogs’ ability to detect urological cancers from the urine of 3000 people. If the results are as good as the pilot trials, dogs will be a lot better at screening than PSA tests.

However accurate they prove to be, the NHS is not going to be putting dogs on the pathology department payroll. It just isn’t practical. But the hope is that if dogs are detecting cancer-specific compounds, scientists can identify them and develop an electronic nose. So dogs are leading us along the way to earlier and more efficient detection, and perhaps from there to insights into the biology of cancer and to new and more effective treatments.

This article first appeared in The Sessional GP magazine.

Judith Harvey

Judith Harvey was a research scientist, ran the VSO programme in Papua New Guinea and taught in a Liverpool comprehensive school before going to medical school. She has been a partner, a salaried GP and a locum, an LMC chair and a long-time supporter NASGP. Her charity, Cuba Medical Link, enables medical students to go to Cuba for their electives.

2 Responses

  1. More roles for our canine friends. A charity takes dogs into care homes and special schools, and a judge in Chelmsford has allowed therapy dogs into court buildings. They find that a minute or two stroking a dog reduces the tension, not just for the person in the dock but for families and witnesses and victims of crimes, and for court staff too.
  2. There's an article in today's Guardian (12th January 2017) about a dog who works at a hospital in Vancouver sniffing out C diff . See https://www.theguardian.com/world/2017/jan/12/clostridium-difficile-infection-canada-dog-detective

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