Abstract

Background: Nowadays, cancer is still one of the main fatal disorders in the world, from which the patients suffer a lot while the burden of the families and society increased. Early recognition and treatment are crucial to reduce the death rate; however, in clinical practice, many cancers could only be recognized when it comes to a later stage. With the development and progress of the modern medical technique, more and more novel testing methods are reported and under research. Many reports showed that dogs could smell out the cancer patients, and exhaled breath test with such as the gas sensor is gradually taking an important role in cancer early diagnosis and screening. However, systematic reviews in both fields are lacking.

Objective: We conducted this review to give an overview on the applications of dog olfactory detection and/or gas analysis technique in cancer early diagnosis and screening.

Method: Chinese National Knowledge Infrastructure (CNKI) and PubMed databases up to August 31st, 2019 were searched to identify relevant studies. All studies related to dog olfactory detection and/or gas analysis products in cancer early diagnosis and screening were summarized and further analyzed. There was no limitation on language of the publication. Data were extracted from all included studies and metaanalysis was performed with Review Manager 5.3. Pooled risk ratios (RR) or mean difference (MD) with 95% CIs were used to evaluate the effectiveness of dog olfactory detection and gas analysis technique application for cancer diagnosis.

Result: 10 dog olfactory detection studies in year 2006-2019 were identified, while the meta-analysis of 2 randomized experiments in dogs showed there was no significant difference between the early cancer diagnosis accuracy of canine scent detection and biopsy-confirmed (p>0.05). No clinical trials of gas analysis technique or product in human were identified, so no meta-analysis could be carried out. Different detection methods and gas analysis products for volatile organic compounds (VOCs) detection were summarized and their features, advantages and disadvantages were reported in detail.

Conclusion: The systematic review indicated that the analysis technique of VOCs from the human exhaled gas has the potential to be used for early cancer screening and diagnosis. The related techniques for VOCs detection are keeping developing, and the accuracy and specificity are continuously improved. However, more high-quality and large-scale randomized clinical trials are needed to confirm the effectiveness of exhaled gas analysis in cancer early diagnosis and screening.