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