Canine cancer detection

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 in the early 1990s has had promising results, no verified studies by secondary research groups have substantiated the validity of this claim.

Background

It is claimed that dogs can detect some substances on the order of parts per trillion, and evolutionary hypotheses explaining the ability of dogs to detect human cancers have been proposed.^[1][2]

Research

Although the first suggestion of this approach in a medical journal, The Lancet, dates back to 1989,^[3] there were only occasional publications on the subject in the next decade.^[4]

However, two studies (one published in 2004^[5][6][7] and one in 2006), involving detection in urine, had promising results, with the 2006 report claiming a 99% accuracy in detecting lung cancer,^[8] 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.^[9] Other studies, also with breath samples, have found promising results.^[10]

Application

There are two proposed benefits, assuming that further studies corroborate the initial results.

• Some researchers believe that dogs will become integrated directly into patient care, akin to their use in detecting bombs and drugs, as well as locating missing people.
• Others recommend that the skill of dogs in detecting cancer would be more appropriately confined to labs, where gas chromatographs could be used to isolate which specific compounds the dogs identified. Recent developments include a simple breathalyser which changes colour according to the compounds in the breath, indicating the presence of cancer.^[11]

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:

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.^[12]

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.^[12]

See also

• Scent hound

References

External links

• Pine Street Foundation - Information and FAQs on Canine Scent Detection of Cancer at pinestreetfoundation.org
• NYTimes - "Dogs Excel on Smell Test to Find Cancer" at The New York Times
• NYTimes - Dogs and Their Fine Noses Find New Career Path at The New York Times
• Dr Dog, the cancer specialistat The Sunday Times
• Dogs Smell Cancer in Patients' Breath at National Geographic
• "Cancer-Detecting Dogs". CNN transcript. February 7, 2006.
• "Man's best friend may hold key to sniffing out certain cancers" at San Francisco Business Times
• "Sniffing out cancer" at Pacific Sun