Canine cancer detection
{{short description|Practice of using dogs' senses of smell to detect cancer}}
{{Alternative medical systems}}
Canine cancer detection is an approach to cancer screening that relies upon the claimed olfactory ability of dogs to detect, in urine or in breath, very low concentrations of the alkanes and aromatic compounds generated by malignant tumors. While some research has been promising, no verified studies by secondary research groups have substantiated the validity of positive, conclusive results.
Background
=Media coverage=
The proposal that dogs can detect cancer attracted widespread coverage in the general media.
In 2015 the Huffington Post reported that studies have suggested that dogs may be able to detect lung cancer, melanoma, breast cancer and bladder cancer, and that dogs can be trained to detect cancer in 93% of cases.{{cite web | url=http://www.huffingtonpost.com/entry/cancer-sniffing-dogs_us_55ed354de4b093be51bbc4bc | title='Groundbreaking' Trial Will Test Cancer-Sniffing Dogs| website=HuffPost| date=2015-09-07}} In 2016, actress Shannen Doherty told Entertainment Tonight in an interview that her dog identified her breast cancer before doctors could diagnose it.{{cite news|last1=Saul|first1=Heather|title=Shannen Doherty says her dog detected her cancer|url=https://www.independent.co.uk/news/people/shannen-doherty-actress-dog-bowie-detected-her-cancer-before-doctors-diagnosed-it-a7169696.html|accessdate=18 December 2016|work=The Independent|date=3 August 2016}} National Geographic said that "man's best friend can detect various cancers, including prostate cancer, colorectal cancer and melanoma."{{cite journal|last1=Langley|first1=Liz|title=How Dogs Can Sniff Out Diabetes and Cancer|journal=National Geographic News|date=19 March 2016|url=http://news.nationalgeographic.com/2016/03/160319-dogs-diabetes-health-cancer-animals-science/|archive-url=https://web.archive.org/web/20160320180419/http://news.nationalgeographic.com/2016/03/160319-dogs-diabetes-health-cancer-animals-science/|url-status=dead|archive-date=March 20, 2016|accessdate=18 December 2016}}
On the other hand, a review by Australian Popular Science found that the more rigorous trials produced less positive results.{{cite journal|last1=Chodosh|first1=Sara|title=The Problem With Cancer Sniffing Dogs|journal=Australian Popular Science|date=5 October 2016|url=http://www.popsci.com.au/science/medicine/the-problem-with-cancer-sniffing-dogs,438728|accessdate=18 December 2016|archive-date=20 December 2016|archive-url=https://web.archive.org/web/20161220192352/http://www.popsci.com.au/science/medicine/the-problem-with-cancer-sniffing-dogs,438728|url-status=dead}} Another trial reported in Nature World News found disappointing results, but nevertheless "the researchers... believe that one day, dogs can still detect lung cancer."{{cite journal|last1=Marucot|first1=Joyce|title=Dogs Can Smell Fear But Can't Detect If You Have Lung Cancer|journal=Nature World News|date=29 September 2016|url=http://www.natureworldnews.com/articles/29386/20160929/dogs-cant-detect-if-you-have-lung-cancer.htm|accessdate=18 December 2016}}
NBC reported that Britain's National Health Service is behind the first clinical trial to test the ability of canines to detect cancer.{{cite web | url=http://www.nbcnews.com/nightly-news/video/these-dogs-are-using-their-noses-to-sniff-out-prostate-cancer-520407107854 | title=These Dogs Are Using Their Noses to Sniff Out Cancer| website=NBC News}}
Research
Although the first suggestion of this approach in a medical journal, The Lancet, dates back to 1989,{{cite journal |vauthors=Williams H, Pembroke A |title=Sniffer dogs in the melanoma clinic? |journal=Lancet |volume=1 |issue=8640 |pages=734 |year=1989 |pmid=2564551 |doi=10.1016/S0140-6736(89)92257-5|s2cid=30238655 }} there were only occasional publications on the subject in the next decade.{{cite journal |vauthors=Church J, Williams H |title=Another sniffer dog for the clinic? |journal=Lancet |volume=358 |issue=9285 |pages=930 |year=2001 |pmid=11575380 |doi=10.1016/S0140-6736(01)06065-2|s2cid=5502581 |doi-access=free }}
However, two studies (one published in 2004{{cite journal |author=Willis CM |title=Olfactory detection of human bladder cancer by dogs: proof of principle study |journal=BMJ |volume=329 |issue=7468 |pages=712–0 |year=2004 |pmid=15388612 |doi=10.1136/bmj.329.7468.712 |pmc=518893 |name-list-style=vanc|author2=Church SM |author3=Guest CM |display-authors=3 |last4=Cook |first4=WA |last5=McCarthy |first5=N |last6=Bransbury |first6=AJ |last7=Church |first7=MR |last8=Church |first8=JC}}{{cite web|url=https://www.usatoday.com/news/health/2004-09-24-cancer-sniffing_x.htm|title=USATODAY.com - Study shows dogs able to smell cancer|work=usatoday.com|accessdate=13 February 2015}}{{cite web|url=https://www.cbsnews.com/news/dogs-can-smell-cancer/|title=Dogs Can Smell Cancer|date=24 September 2004|work=cbsnews.com|access-date=13 February 2015}} and one in 2006), involving detection in urine, had promising results, with the 2006 report claiming a 99% accuracy in detecting lung cancer,{{cite journal |vauthors=McCulloch M, Jezierski T, Broffman M, Hubbard A, Turner K, Janecki T |title=Diagnostic accuracy of canine scent detection in early- and late-stage lung and breast cancers |journal=Integrative Cancer Therapies |volume=5 |issue=1 |pages=30–9 |year=2006 |pmid=16484712 |doi=10.1177/1534735405285096|doi-access=free }} although both studies were preliminary and involved small numbers of patients.
In a 2011 study, lung cancer was identified with a sensitivity of 71% and a specificity of 93%, using breath samples.{{cite journal |vauthors=Ehmann R, Boedeker E, Friedrich U |title=Canine scent detection in the diagnosis of lung cancer: Revisiting a puzzling phenomenon |journal=Eur Respir J |volume= 39|issue= 3|pages= 669–76|date=August 2011 |pmid=21852337 |doi=10.1183/09031936.00051711 |url=http://erj.ersjournals.com/content/early/2011/08/05/09031936.00051711.abstract?sid=b4c367ac-6264-4d94-8b46-2b1505bb3fcf|display-authors=etal|doi-access=free }}
Skeptical analysis
In a May 25, 2012 article, “What to make of Medical Dogs” published by Science-Based Medicine, Peter Lipson reported on his review of the scientific literature regarding these claims and found valid support for positive conclusions to be lacking:
{{quote|text=While anecdotes abound, there is scant literature to support this ability. One unimpressive pilot study looked at dogs’ potential ability to detect bladder cancers from urine samples. The idea behind cancer dogs is that there may be volatile compounds produced in cancer patients that dogs can detect by scent. In these studies, the compounds are not identified, not tested for, not named. There are many confounders, for example, in the few samples used, there may be other differences being detected by the dogs.{{cite news|last1=Lipson|first1=Peter|title=What to make of Medical Dogs|url=https://www.sciencebasedmedicine.org/what-to-make-of-medical-dogs/|newspaper=Science-Based Medicine|date=25 May 2012|accessdate=5 October 2016}}}}
{{quote|text=In the other study (I found very few) dogs were “trained” to detect lung and breast cancers in humans. The methodology of breath sampling is not validated as far as I can see, and once again, the putative compounds in breath are not identified. Statistically, the efficacy is marginal at best… I don’t doubt the social and emotional value of dogs as companions, and as active helpers in many circumstances. But beyond this, the evidence is wanting.}}