Dogs Sniff Out Lung Cancer in Humans

November 12, 2012

Dogs Sniff Out Lung Cancer in Humans

Recent research coming from Germany states that dogs can smell lung cancer successfully to an acceptable level of accuracy. The study, which is published in the European Respiratory Journal, notes that the level was far higher than that of chance (14%). The four specially trained dogs correctly identified cancer in 71 out of 100 cases. They were also successful when excluding cancer. From 400 samples known to be cancer free, they successfully ruled out 372 as not having cancer. That means that their failure rate was only about 7%. This has led German researchers to say that the four specially trained dogs, two German shepherds, an Australian shepherd, and a Labrador retriever can ‘reliably sniff out lung cancer in human breath’.

Because lung cancer has few symptoms in its early stages of development it makes diagnosis difficult. This is the time when treatment would be easier and more successful. “This is the holy grail,” says Suresh S. Ramalingam, MD, associate professor and director of the lung program at Emory University’s Winship Cancer Institute in Atlanta. “The whole field is focused on using something that’s readily available that does not involve an expensive surgery or scan that would allow us to find early cancers”. Ramalingam is presently working on developing technology which can sense and identify chemicals produced by cancerous tumors. He is looking for a technology based answer to copy the dogs’ sense of smell. He was not involved in the research.

Examining Patients for Cancer

The dogs sensitivity in the tests exceeded the success rate of chest computed tomography (CT scan). Their success rate was also higher than a bronchoscopy, which although not a major operation is still considered to be an invasive procedure requiring anesthesia of some kind.

There is strong anecdotal evidence to state that dogs can sense something untoward in their owners. There have been reported cases in which owners have been alerted to an illness because of the dog’s behaviour. Perhaps continually pawing or licking one place on the body. Later it has been found that is where the undiagnosed cancer has been. Dogs can even be trained to sense low blood sugar levels in diabetes sufferers.

Another study published in the BMJ in 2004 found that dogs could correctly identify bladder cancer on average about 40% of the time, this rate was better than the 14% accuracy that one would expect randomly. However it was lower than other available tests at that time.

But earlier this year Japanese researchers reported that dogs could identify signs of colon cancer from human breath and stool samples. It was stated that the accuracy was almost 90%, this is only a little lower than a colonoscopy.

Test Formats

There are many different results to differing tests for different types of cancer. This is an issue, there is no consistency. In some studies the dogs were trained for nine months whilst other studies have used dogs with only three weeks training.

No one has conclusive evidence yet as to what is the best sample type to provide to the animals. The dogs all had varying degrees of success depending on whether they were smelling samples of urine, breath, blood, or stool. However dogs have had more success when the studies are carefully controlled.

The method of study and the rigours imposed on the researchers are all relevant. In one study 220 volunteers were used. The group was broken into three subgroups, 110 were healthy, 60 had lung cancer, and 50 suffered from chronic obstructive pulmonary disease (COPD). All were asked to exhale into a glass tube filled with fleece.

A procedure was in place to ensure that those who handled the dogs did not know who the samples came from to ensure that no inadvertent signals came from the handler. The dogs were only shown a small amount at a time and only one cancer sample was present at anytime. This ensured that the testing took place in as controlled a manner as was possible. We are not always aware of control factors in every study.

The findings of this particular study indicated that the dogs appeared to accurately identify the samples from cancer patients, even when they were in very early stages of the disease. They successfully chose the cancer patient’s sample despite any other smells such as cigarettes or food being present.

Longtime smokers at high risk for lung cancer who received annual rapid computed tomography (CT) scans of their lungs cut their risk of dying of the disease by 20% it was noted by a government funded study. However because it falsely detects cancer 25% of the time extra invasive surgery is taking place when it is not required. This test has caused some controversy.

How Dogs Detect Cancer

Most researchers accept that dogs can detect diseases by smelling something. Identifying that ’something’ is the aim. “We know that it can be done, we have seen the dogs doing it but we must identify what it is the dogs are sniffing to ensure that procedures are conducted in a regulated and scientific manner” is a general comment from those involved.

The latest research appears to be homing in on volatile organic compounds (VOCs). These VOCs can be thought of as our breath’s signature and over 4,000 VOCs can be present in a person’s breath. The chemical compositions of VOCs vary depending on the health of the body and it is this change that interests the researchers.

Experts say that a dog’s nose is between 100 and 1,000 times more sensitive than a human nose. This superiority allows the dog to smell chemicals present in the VOCs because of a cancer (or other disease) being present in the body. Having a sensitive nose alone is not the answer. It is how to identify the risky smells and alert the humans to their presence. An aim of many researchers is to identify what it is the dogs know about and then replicate it in an automated fashion. This is because the success rates identifying cancer vary between dogs. The real work should take place because we know that dogs can detect cancer but it may take technology to reliably increase the success rate.

How Dogs Detect Cancer

Most researchers accept that dogs can detect diseases by smelling something. Identifying that ’something’ is the aim. “We know that it can be done, we have seen the dogs doing it but we must identify what it is the dogs are sniffing to ensure that procedures are conducted in a regulated and scientific manner” is a general comment from those involved.

The latest research appears to be homing in on volatile organic compounds (VOCs). These VOCs can be thought of as our breath’s signature and over 4,000 VOCs can be present in a person’s breath. The chemical compositions of VOCs vary depending on the health of the body and it is this change that interests the researchers.

Experts say that a dog’s nose is between 100 and 1,000 times more sensitive than a human nose. This superiority allows the dog to smell chemicals present in the VOCs because of a cancer (or other disease) being present in the body. Having a sensitive nose alone is not the answer. It is how to identify the risky smells and alert the humans to their presence. An aim of many researchers is to identify what it is the dogs know about and then replicate it in an automated fashion. This is because the success rates identifying cancer vary between dogs. The real work should take place because we know that dogs can detect cancer but it may take technology to reliably increase the success rate.

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