Dogs can reliably sniff out lung cancer, according to a study carried out by a group of doctors from Stuttgart. The study shows that a dog can accurately detect cancer-specific components by sniffing human breath.
The project was started on the initiative of Dr. Rainer Ehmann, a lung specialist who runs an out-patient pneumology clinic in Stuttgart, along with two colleagues. Ehmann read about a prospective American study undertaken in 2006 that showed that sniffer dogs are able to reliably detect lung and breast cancers in human breath. Ehmann developed the idea further and reasoned that dogs might also be able to differentiate lung cancer from other respiratory diseases, in particular COPD (chronic obstructive pulmonary disease), something that modern electronic tests (“electronic noses”) are unable to do. Electronic noses also fail to detect such diseases in the breath of smokers, probably due to the large number of other harmful substances present.
Ehmann contacted Uwe Friedrich, a dog trainer from the city of Löffingen (Black Forest, Germany), who agreed to participate in the investigations. As Ehmann was unable to collect as many breath samples as he would have needed to carry out a statistically founded study, he started looking for partners and got a positive response from doctors at the Schillerhöhe Hospital in Stuttgart, which is part of the Robert Bosch Hospital. Ehmann presented his ideas to PD Dr. Thorsten Walles who, despite being somewhat sceptical, agreed to work with Ehmann as he was keen to be able to refute the hypothesis that dogs are able to sniff out lung cancer-specific components from human breath. The two doctors set up a team and designed a study to investigate the hypothesis in detail. “The three of us made an excellent team. I dealt with the preliminary tasks and planning, while Dr. Walles dealt with the scientific organisation of the study and Uwe Friedrich organised the relevant training for the dogs,” explained Ehmann.
Not all breeds of dog are as good as others when it comes to being sniffer dogs. Ehmann explains: “Dogs like Pekingese that have difficulties breathing are unsuitable for the project. In general, dogs with a longer snout are particularly well suited as sniffer dogs. I believe this is because the smell can develop a lot better in their longer noses, rather like red wine, where the aroma develops a lot better in broader glasses than thin ones. The dogs must also have a good level of concentration because detection work is very exhausting for them. This is why dogs with any sort of “attention deficiency disorder” equivalent were excluded from the study. In the search for suitable four-legged “colleagues”, Friedrich spoke to people he knew, friends and clients. “All of our dogs were family dogs because the dogs and their owners loved the work,” said Ehmann highlighting that fun was a major aspect in this particular challenge and that the dogs’ owners spent every weekend training for the upcoming diagnostic work.
The study involved breath from lung cancer patients from the Schillerhöhe Hospital. The volunteers exhaled into glass tubes filled with fleece soaked in silicone to enable it to bind the volatile hydrophobic and hydrophilic compounds in the breath. The dogs were then trained to identify the compounds. The study was published online in the European Respiratory Journal in August 2011, and the outcome was fairly spectacular: the dogs successfully identified 71 samples of lung cancer out of a possible 100. They also correctly detected 93 percent of the samples that did not have lung cancer. “We worked with volunteers, who were rated healthy according to basic diagnostics, and selected patients according to standard clinical criteria,” said Ehmann. The dogs were able to reliably detect cancer even in the presence of other factors like tobacco smoke, food smells and COPD. It is highly likely that dogs would be able to reliably detect other sorts of tumours, as it is still not known which of the cancer- and lung cancer-specific compounds they can actually smell. It is therefore likely that dogs can sniff out more diseases than human beings are able to diagnose. Walles is now convinced that dogs are reliable cancer sniffers and he will continue to work with Ehman in the search for specific organic volatile compounds associated with the presence of cancer.
“We do not yet know which volatile compound is a sign of cancer. Breath contains around 3500 organic volatile compounds (VOCs) and we initially assumed that one of them is associated with the presence of cancer, i.e. results from the metabolism of lung cancer cells,” said Ehmann who is now unsure whether the search for lung cancer markers involves one or more VOCs. “Since the study was published, scientists all over the world including biochemists have contributed their ideas and viable thoughts about which compound it could be. We now assume that the presence of lung cancer is associated with more than just one VOC and that the dogs detect a VOC pattern,” said Ehmann who, together with Walles, will investigate the issue further using two different approaches.
Dr. Enole Boedeker from Dr. Walles’ team in the Schillerhöhe Hospital is currently investigating whether the dogs specifically detect lung cancer or whether they can detect cancer in general. The scientists will also investigate whether the dogs are able to sniff out breast and ovarian cancer. Ehmann himself is planning to carry out studies on coin lesions. “Coin lesions are small, circular lung alterations that are less then three centimetres in diameter and can be detected with X-rays and to an even greater extent with computer tomography. Almost 20 per cent of all people have small circular pulmonary lesions, the majority of which are benign and harmless in people who do not smoke,” said Ehmann explaining that the removal of such lesions was nevertheless standard practice a couple of years ago, but has now become less frequent in order to avoid stressful surgery. People with coin lesions now tend to undergo regular monitoring for around two years, which can cause major psychological stress. “If the lesion does not grow during the time it is monitored, the patient is given a clean bill of health despite the fact that there is no absolute certainty. Tumours can remain unchanged for many years and suddenly start to grow again. In addition, many lung tumours metastasise at a very early stage,” said Ehmann pointing out that the use of sniffer dogs would make the early detection of lung cancer more reliable.
Ehmann is now looking for sponsors for the coin lesion study. He hopes to be able to establish lung cancer diagnostics with dogs despite the fact that there has been some criticism from doctors. “Is the breed of dog we are using a reliable one? I think it is. Of course, dogs are not machines that can be calibrated, but they can be one of several “tools” in lung cancer diagnosis,” said Ehmann.
Dr. med. Rainer Ehmann
Ambulante Pneumologie mit Allergiezentrum
Tel.: +49 (0)711/ 6070 401
Fax: +49 (0)711/ 6070 400