Can dogs smell lung cancer? First study using exhaled breath and urine screening in unselected patients with suspected lung cancer

Background. On the basis of our own experience and literature search, we hypothesised that a canine olfactory test may be useful for detecting lung cancer in an unselected population of patients suspected to have lung cancer. Material and methods. We conducted a prospective study of 93 patients consecutively admitted to hospital with suspected lung cancer. Exhaled breath and urine were sampled before the patients underwent bronchoscopy. The canine olfactory test was performed in a double-blinded manner. Sensitivity and specificity were outcome measures. Results. With 99% sensitivity, the olfactory test demonstrated that dogs have the ability to distinguish cancer patients from healthy individuals. With an intensified training procedure, the exhaled breath and urine tests showed sensitivity rates of 56-76% and specificity rates of 8.3-33.3%, respectively, in our heterogeneous study population. Conclusion. Although the olfactory test appears to be a promising tool for the detection of cancer, the main challenge is to determine whether the test can sufficiently discriminate between patients at risk, patients with benign disease, and patients with malignant disease. We need to gain a deeper understanding of this test and further refine it before applying it as a screening tool for lung cancer in clinical settings.