Dogs capable of sniffing out prostate cancer

They're known as man's best

friend; but dogs could soon also

be their greatest ally in the fight

against prostate cancer. Britain's

National Health Service recently

approved a trial for dogs capable

of sniffing out prostate cancer in

the hope that it could show up

inaccuracies in the current PSA

(prostate specific antigen) test.

Fantastic sense of smell

It's 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 – three-hundred

million sensory receptors, while

humans have only five million. 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,"

said Dr Claire Guest who co-

founded charity Medical

Detection Dogs in 2008 to train

specialist dogs to detect human

diseases.

She added 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.

Almost instant detection

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."

Medical Detection Dogs gained

approval from Milton Keynes

University Hospital for further

trials, after initial testing showed

trained dogs can detect prostate

tumours in urine in 93 percent 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 says dogs can detect the

scent of cancer almost instantly,

meaning they could potentially

check many more samples than a

human could possibly do.

A hunt game

"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 11 years old, is one of the

dogs taking part in the trials in

Milton Keynes.

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.

An electronic nose

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.

While many dog-lovers may think

it would be nice to have a dog in

every doctor's surgery to screen

for cancer, ultimately that is not

practical. Instead the scientists

hope their research will lead to

the invention of an electronic

nose that will mimic that of a

dog's.

"Ultimately we hope to use the

information that the dogs

produce to actually develop an

electronic nose. So eventually you

could have a machine that sits on

your consultant's desk, you'd put

the urine sample in it and it

would tell you if it was positive

or negative. That would be the

ultimate aim," added Fletcher.

However, a viable "electronic

nose" is still many years away,

with no technology able to get

close to the sniffing power of

man's four-legged friend.

"The problem the electronic nose

scientist has is that currently

their sensitivity is well below the

dog. A dog can find parts per

trillion; we had an electronic

nose working alongside the

dogs recently and they were

unable to find anything below

parts per million," said Dr Guest.

- Reuters

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