cancer is not the death sentence it once was. Early diagnosis and better cancer treatments have a significant impact on outcomes. The use of the sense of smell as an indicator of human diseases probably originated with Hippocrates. Dogs are well known for their incredible sense of smell and research have done in leading universities throughout the world have shown amazing results. The successful results of clinical trials in which breath or other human samples were used to detect diseases by dogs are accumulated over the recent years. All those studies suggest that dogs can be used as cancer detectors thanks to their extraordinary sense of smell with odour detection thresholds as low as parts per trillion.
McCullon et al. showed results of dog's detections of exhaled samples with a sensitivity of 0.99 and specificity of 0.99 for lung cancer samples, and a sensitivity of 0.88 and a specificity of 0.98 for breast cancer samples.
A study from 2017, conducted by Hector Guerrero-Flores shows the success of dogs to identify Cervical Cancer (CC) from fresh cervical smear samples with high specificity and sensitivity values >90%. This data supports the use of trained dogs as a viable, affordable, non-invasive and therefore, a highly relevant alternative method for detection of CC lesions.
More supporting evidence for dogs detecting prostate cancer has been published including a study by Cornu and colleagues indicated the possibilities of canine cancer detection of prostate cancer (sensitivity 91%, specificity 91%).
Taverna et al. from Italy reported the diagnostic accuracy of dogs trained to recognize specific volatile organic compounds of prostate cancer in urine samples (sensitivity 98--100%, specificity 98--99%).
A study that was published in 2011 by Sonoda and colleagues investigated colorectal cancer screening using stool samples and demonstrated promising results (sensitivity 97%, specificity 99%) in this study the canine scent detection was not confounded by current smoking, benign colorectal disease or inflammatory disease.