Dogs can sniff out bowel cancer in breath and stool samples, with a
very high degree of accuracy - even in the early stages of the
disease - reveals research published online in the
journal Gut.
The findings prompt the authors to suggest that chemical compounds
for specific cancers circulate throughout the body, which opens up
the prospect of developing tests to pick up the disease before it
has had the chance to spread elsewhere.
A specially trained Labrador retriever completed 74 sniff tests,
each comprising five breath (100 to 200 ml) or stool samples (50
ml) at a time, only one of which was cancerous, over a period of
several months.
The samples came from 48 people with confirmed bowel cancer and 258
volunteers with no bowel cancer or who had had cancer in the
past.
Around half of the volunteer samples came from people with bowel
polyps, which although benign, are considered to be a precursor of
bowel cancer. And 6% of the breath samples and one in 10 of the
stool samples from this group came from those with other gut
problems, such as inflammatory bowel disease, ulcers,
diverticulitis, and appendicitis.
The bowel cancer samples came from patients with varying stages of
disease, including early stage.
The dog successfully identified which samples were cancerous, and
which were not, in 33 out of 36 breath tests and in 37 out of 38
stool tests, with the highest detection rates among those samples
taken from people with early stage disease.
This equates to 95% accuracy, overall, for the breath test and 98%
accuracy for the stool test, compared with conventional colonoscopy
- a procedure involving a tube with a camera on the end inserted
through the back passage.
Samples from smokers or from those with other types of gut
problems, which might be expected to mask or interfere with other
smells, did not pose a problem for the dog.
This indicates that there are specific discernible odours given off
by cancer cells which circulate around the body, say the authors.
And it is backed up by other research and anecdotal evidence
indicating that dogs can sniff out bladder, skin, lung, breast and
ovarian cancers, they add.
The authors concede that using dogs to screen for cancers is likely
to be impractical and expensive, but a sensor could be developed to
detect the specific compounds.
The faecal occult blood test, which picks up hidden blood in a
stool sample is an effective and non-invasive method of screening
for bowel cancer, say the authors, but it is only able to pick up
early stage disease in one in 10 cases.
"Early detection and early treatment are critical for the
successful treatment of cancer and are excellent means for reducing
both the economic burden and mortality [of bowel cancer]," comment
the authors.
###
Thanks to
BMJ-British Medical Journal for this article.