Detecting Early Stage Lung Cancer May Become a Clinical Function of Sniffer Dogs |

Detecting Early Stage Lung Cancer May Become a Clinical Function of Sniffer Dogs
Lung cancer is one of the most deadly cancers, and one that all too often is not detected early enough for treatment to be effective. Although progress is being made, as discussed in the papers below, standard x-rays often fail to detect lung cancer early enough for any therapy to be successful. The fact that dogs are fairly good at detecting a significant proportion of lung cancers thus makes their use in a clinical setting a real possibility. As one of the studies discussed below concludes, canine cancer detection is “virtually on the verge of respectability.” Whether or when dogs will be used to screen us for lung cancer remains uncertain, but recent research indicates that the odds are going up in favor of this canine skill having practical application in the future.

I had speculated, as had Mary Elizabeth Thurston even earlier (1996), that remoteness might drive the use of dogs in cancer detection into clinical reality. The argument was made that dogs could become a tool of Doctors without Borders or doctors who fly to remote Arctic villages. Now it appears that the possibility of early detection by canines of cancers that are particularly difficult to find at asymptomatic stages may be the factor that brings dogs into actual diagnostic settings. This blog describes several articles, but the pictures were supplied by Dr. Tadeusz Jezierski of the Polish Academy of Sciences.

Dogs Distinguish Lung Cancer Patients from Healthy and COPD Patients

Breath Sample Tube

A team in Stuttgart, Germany (Ehmann et al., 2012), used four family dogs (two German shepherds, one Australian shepherd, and one Labrador retriever), two males and two females, all between 2.5 and 3 years old. All were trained to indicate to breath samples of patients with lung cancer by lying on the floor in front of the test tube and resting the muzzle against the tube.Training involved the dogs distinguishing breath samples of healthy volunteers from those of patients with lung cancer. No training was performed to distinguish COPD samples.

The researchers collected 220 breath samples from patients with COPD (50) or lung cancer (60), as well as from healthy individuals (110). Dogs were presented with five probes position in five separate retainers on the floor, rubber caps removed. The position of the probe with lung cancer was determined randomly and was blind to the participants except those who set up the probes.

The dogs did not perform identically, but each performed consistently. The accuracy of a dog’s indication did not favor advanced tumor stages. “The overall sensitivity was 71% and the specificity was 93%....” That is, the dogs identified 71% of the breath samples of those with cancer, and incorrectly found cancer in only 7% of the individuals who did not have cancer. The table, adapted from one included in the study, illustrates how specificity and sensitivity are calculated.

	Breath sample without cancer	Breath sample with confirmed LC	Total
Dogs indicating presence of LC	28	71	99
Dogs indicting absence of LC	372	29	401
Total	400	100	500
Specificity	372/400 = 93%
Sensitivity		71/100 = 71%

The researchers concluded that there is “a stable marker (or scent pattern) that is strongly associated with LC [lung cancer] and independent from COPD, but can be reliably discriminated from tobacco smoke, food odors and (potential) drug metabolites.” They argue that sniffer dogs as cancer detectors are “virtually on the verge of respectability.”

What the dogs are identifying, according to the Stuttgart group, remains speculative. They note that 3,481 volatile organic compounds have been described in human breath, mostly in amounts of particles per trillion. Which ones increase because of lung cancer is only beginning to be described. Recent studies have succeeded in distinguishing healthy from cancerous breath by electronic nose technology. In these recent results, tumor stage did not influence the outcome in any of the studies, “implying that exhaled breath profiling has the potential to evolve as a screening test for LC—once specific markers have been identified.” They add that “it is currently difficult to predict when a clinically applicable diagnostic device for breath analysis will be available.”

As to specific chemicals the researchers noted that “Metropolol, Verapamil and Tiotropiumbromide were consistently distributed between LC and COPD patients, but not found in healthy volunteers. Marcumar, Clopidogrel and Ezetimib were present exclusively in COPD patients.”

As to COPD, the researchers note:

“COPD often precedes and accompanies LC in smoking patients…. COPD is characterized by typical lung function deterioration, chronic systemic and local airway inflammation and structural changes in lung parenchyma. It has been shown that the level of exhaled biomarkers is altered in patients with COPD compared to healthy control subjects…. Moreover, since the development of LC is much more frequent in COPD patients than in healthy controls, attention needs to be focused on the subtle differences in exhaled biomarker profiles between LC and COPD.”

Study Compares Dogs and Machines

As noted by Buszewski et al. (2012b), a sweetish, acetone-like breath odor indicates a person has diabetes, while the odor of rotten eggs, caused by organic sulfide and thiol compounds, suggests liver disease. Chemical analysis requires being able to deal with very low concentrations of chemicals exhaled so certain procedures must be used before analysis. The most common method of enriching volatile organic compounds involves solid-phase microextraction followed by analysis by gas chromatography (GC) or GC-mass spectrometry (GC-MS).

Taking Breath Sample

Exhaled air consists of alveolar air, which has been in contact with blood inside the alveoli, and ambient air, retained in the mouth, nose, pharynx, trachea, and bronchi. Alveolar air is strongest as the end of expiration of breath.

A chemical sensory approach, gas chromatography and mass spectrometry (GC-MS) for cancer screening was, in a second paper by the Polish team, Buszewski et al. (2012a), compared with using dogs to detect cancer. The GC-MS approach allows for specificity in the chemicals—volatile organic co

Detecting Early Stage Lung Cancer May Become a Clinical Function of Sniffer Dogs