Dogs can detect scent of early stage bowel cancer
7 Feb 2011
Dogs can detect the scent of bowel cancer in both breath and
stool samples with a very high degree of accuracy, even in the early
stages of the disease, according to Japanese research published
online in the journal Gut .
The authors conclude that there is a specific cancer scent and
that chemical compounds for specific cancers circulate throughout
the body. This opens up the prospect of developing tests to pick up
the disease before it has had the chance to spread elsewhere.
The researchers used a specially trained Labrador retriever. It
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
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
1. Sonoda H, Kohnoe S, Yamazato T, et al. Colorectal cancer
screening with odour material by canine scent detection. Gut (2011).