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Diagnostic Accuracy of Canine Scent Detection of Lung and Breast Cancers
in Exhaled Breath
The following research was published in the March
2006 issue of Integrative
Cancer Therapies, a peer-reviewed journal.
» Download a full, free
copy of this study by clicking
here: PDF [104kb]
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the journal's Press
Release.
» See media clippings about this research.
» Read the Frequently Asked Questions.
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ABOUT THIS RESEARCH, BRIEFLY
Lung cancer, when symptoms arise, is usually diagnosed at Stage III
or IV, when the prognosis is rarely good. Treatment is significantly
more effective at early stages (I or II) when the tumor is smaller and
has not yet spread. Detecting lung cancer in its early stages is difficult,
so therefore developing a feasible and effective early detection method
is the subject of a considerable amount of research around the world.
In terms of breast cancer, while detection at early stages is comparatively
easier, finding methods to detect it even earlier are worthwhile.
In a large international collaboration, the Pine Street Foundation conceived
of and obtained grant support for a rigorously designed diagnostic study
aimed at accurate early detection of lung and breast cancers. We invited
scientist Professor Tadeusz Jezierski, ScD, of the Polish Academy of
Sciences, to serve as principal investigator for this study.
A dog's nose, considered by both dog trainers and chemists alike to
be one of the world's most powerful olfactory sensor, was the "medical
device" used in this research. In a study of 86 people (55 with
lung cancer and 31 with breast cancer), five professionally trained scent
dogs accurately distinguished between breath samples from diseased patients
and those from 83 healthy controls. The dogs' ability to correctly identify
or rule-out
lung and breast cancer, at both early and late stages, was around 90%.
A more exact and specific discussion of the sensitivity and specificity
of the dogs' abilities is available in the full
study.
This work is based on the hypothesis that cancer cells emit different
metabolic waste products than normal cells. The differences between these
metabolic products are apparently so great that they can be detected
by a dog's keen sense of smell, even in the early stages of disease.
In carefully controlled conditions, the dogs were presented with breath
samples of both cancer patients and healthy controls. The dogs were trained
by professional dog behaviorist Kirk Turner and the methods used in the
field research were developed by Professor Jezierski. Not only did the
dogs perform exceptionally well, they did so consistently over a lengthy
four month investigation of 12,295 separate scent trials - each one documented
on videotape.
What is important about this study is that (1) ordinary dogs, with no
prior scent discrimination training, could be rapidly trained to identify
lung and breast cancer patients by smelling samples of their breath,
when compared to blank unused sample tubes; (2) dogs could accurately
and reliably distinguish breath samples of lung and breast cancer patients
from those of healthy controls; and (3) the dog's diagnostic performance
was not affected by disease stage of cancer patients, age, smoking, or
most recently eaten meal among either cancer patients or controls.
NEXT STEPS
We are actively seeking funding to launch new studies that will build upon
this research. This pilot work using canine scent detection demonstrates
the validity of using a biological system to examine exhaled breath in the
diagnostic identification of lung and breast cancers. Future work will closely
examine the chemistry of exhaled breath to identify which chemical compounds
can most accurately identify the presence of cancer. A prospective cohort
study, comparing both biological (canine scent detection) and chemical methods
to conventional diagnosis within a given set of individuals, should help
answer the question of whether these approaches can lead to changes in how
cancer in diagnosed in clinical practice.
Another goal is to study canine scent detection of ovarian cancer,
a disease that is currently very difficult to detect at its earliest
stages.
INFORMED CONSENT & ANIMAL SAFETY
All subjects provided written informed
consent and our protocol and patient recruitment materials were approved
by an independent Institutional Review Board (Independent Review Consulting,
Corte Madera, Calif.). Additionally, our animal training
and handling methods
were designed in consultation with two veterinarians, an independent
dog trainer, and the dog owners themselves, all of whom approved our
methods. We used food reward-based positive reinforcement training, also
known as clicker training; no compulsion training methods were ever used.
None
of the animals were ever harmed, either physically or psychologically,
in the course of this research; the health, safety, and happiness of
all the animals involved was always our first priority. We did not provide
any compensation to subjects for providing breath
samples
or to dog owners for volunteering use of their dogs in the study.
GRANT SUPPORT
This research was made possible through the generous
support of the MACH Foundation (Fairfax, Calif.) and Frank
and Carol Rosenmayr (Kentfield, Calif.). Their support allowed us
to invite Dr. Jezierski to work
with us for four months and to
provide
our team of trainers and volunteers with methodical guidance and
close supervision. Study sponsors had no role in study design, data collection,
data analysis, data interpretation, manuscript preparation, or the
decision to publish. We would also like to acknowledge Guide Dogs
for the Blind (San Rafael, Calif.) for their help in making
dogs available for this study.
HOW YOU CAN GET INVOLVED
There are many ways you can help us to further research in this emerging
field:
» Funding.
Support from individuals is incredibly important. If you are
interested in continuing this research, please make
a donation. 92% of our funding comes from individuals like you. Additionally,
should you know of any foundations or individuals who might also be interested
in supporting us, please pass the word along.
» Replicate Our Study. For researchers, we actively encourage you
to learn more about our current study and to build and improve upon
it
through
new research.
» Get the Word Out. The more people who know about this work,
the better. Please
share us with your friends and colleagues.
FREQUENTLY ASKED QUESTIONS
Was this research published in a peer-reviewed journal?
Yes. Our research was rigorously peer-reviewed prior to publication
in
Integrative Cancer Therapies, which is a peer-reviewed journal
indexed in MEDLINE.
Are the dogs smelling cancer or just people?
Dogs and patients did not meet directly. We gathered breath samples
in specially designed tubes and then, at a separate location, presented
those tubes to the dogs for training and testing. Additionally, during
the entire double-blinded testing phase, upon which our data is based,
all breath samples sniffed by dogs, for both cases and controls, were
from completely different subjects not previously encountered by the
dogs during training or single-blinded testing.
What about the smells
of smoking?
Smokers were present in both lung cancer patients and the control groups.
The strong results we found remained even after accounting for confounding
by smoking in our analysis.
What about the effect of chemotherapy on body odor?
Breath samples were taken before starting conventional treatment.
Weren't the cases and controls very different
from each other?
Yes. This is correct and a valid criticism of our study. In the long course
of developing a new diagnostic method, the first step is to see if the method
can distinguish known cases from controls. This preliminary step is then followed
by testing in which the new method is compared head-to-head with existing diagnostic
methods and then examining people whose true health status is not known at
the time of the study.
Do you really expect dogs to be used in hospitals to detect cancer?
Our study provides compelling evidence that cancers hidden deep within
the body can be detected simply by examining the odors of a person's
breath. The fact that it was dogs who did this does not detract from
the novelty of our findings. The dog's brain and nose is currently one
of the most sophisticated odor detection devices on the planet...technology
now has to rise to meet that challenge and it remains to be seen whether
chemical analysis can meet the level of the dogs.
What are the next steps?
The direction our research is taking, and should take, is toward the
development of an "electronic nose". This sort of device would
be much more likely to be incorporated into clinical practice. In the
end, diagnostic breath analysis deserves further rigorous study, both
through additional work with dogs and through chemical analysis towards
the goal of understanding precisely what compounds it is that the dogs
are detecting by scent. These are the questions our next generation trial
will address, and for which we are currently seeking funding.
What sorts of dogs did you use in this study? What were your selection
criteria?
Five dogs, ages 7-18 months, were chosen out of a total of 13: three
Labrador retrievers (two males and one female) and two Portuguese water
dogs (one male and one female). Dogs were provided by local dog owners
and by Guide Dogs for the Blind in San Rafael, Calif. Our selection
criteria called for dogs over six months old with basic obedience training
typically
given to household pets, as defined by the American Kennel Club, who
were judged by the experimenters to be eager to sniff objects and respond
to commands.
What were the names of the dogs?
Kobi: Labrador retriever (yellow)
Isabelle: Portuguese water dog
Court: Labrador retriever (black)
Estelle: Labrador retriever (yellow)
Django: Portuguese water dog
How can I get my dog involved in your research?
Should we receive funding to continue research in this field, we will
likely be recruiting additional dogs from the San Francisco Bay
Area.
An announcement will be made through our newsletter, so be sure to
sign up to receive email updates. Additionally, the Pine Street Foundation
is available to discuss this research with individuals or groups who
may be interested in pursuing a collaboration leading toward grant-funded
clinical research.
Can I have your dogs screen me to see if I have cancer?
Unfortunately,
it is not currently possible to be "screened" by the dogs
involved in our research. At this time, it is also not recommended that dogs
be used as a primary screening method for cancer. It is our hope, however,
that the
concepts
explored
in our research may help develop more accurate cancer screening methods in
the future. Nevertheless, numerous anecdotal reports have been published and
televised documenting individual cases in which dogs began to display persistent
and animated behavior around specific body locations on their owners. These
behaviors, on subsequent medical evaluation, proved to be accurate, and in
some cases life-saving, early warning signs of cancers such as those of the
breast and skin (melanoma). Therefore, should your dog display such behavior,
we do recommend medical follow-up.
How can I train my dog to detect cancer?
The methods used in our study are similar to how you might train your
dog to sit or roll over. We specifically used "clicker training",
a reward-based method of teaching in which the dog is given food treats
for offering the desired behavior. What is more difficult is obtaining
breath samples from cancer patients; there are various
state
and federal
requirements regarding medical research that must be followed. There
are also important ethical and scientific issues that must be addressed
before engaging in this type of training. For example, what would a
person
do with
the dog after training is complete? Would the dog be used to screen
people
for cancer? How would the dogs' accuracy
and consistency be determined? What
would
a person who is screened then do with
the information
gleaned from the dogs? Could or should the results be trusted?
Worse than a false positive (where
a dog indicates there is
cancer present when no disease actually exists) would be a false negative
(where the
dog indicates
no cancer
is present when in fact there is disease). Because of the various
logistical and ethical considerations
associated with this type of research, it is recommended that
individuals engaging in this type of training follow appropriate
scientific and ethical guidelines such as those documented in our study.
Additionally,
the Pine Street Foundation is available to discuss this research
with individuals or groups who may be interested in pursuing a collaboration
leading
toward grant-funded clinical research.
QUESTIONS AND COMMENTS
Have comments or additional questions? Please contact
us.
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