PTU-072 Breath testing for colorectal polyps and cancer- a load of hot air?

Abstract

Introduction Colorectal cancer (CRC) is the 2nd most common UK cause of cancer death. The bowel cancer screening programme (BCSP) targets those aged 60–74, but is dependent upon uptake. Some colonoscopies may be unnecessary and are not without risk. A breath test could be a useful tool for triaging for colonoscopy those without red-flag symptoms, or possibly for screening for advanced polyps and cancer. Prior studies have shown promising results of a breath test using exhaled propanal for detecting CRC (96% sensitivity/76% specificity). The Colorectal BReath Analysis (COBRA) study aims to determine the diagnostic accuracy of breath VOCs for detecting CRC and adenomatous polyps. Methods COBRA is an ongoing prospective cohort study of 2000 patients attending for colonscopies across 4 London BCSP centres. Exhaled breath (500 mls) is collected using the ReCIVA breath sampling device, onto 4 thermal desorption (TD) tubes. Analysis by gas chromatography mass spectrometry (GCMS) and proton transfer reaction mass spectrometry (PTRMS) identifies and quantifies breath compounds, at St Mary’s Hospital VOC laboratory. Polyp risk classification is determined using the BSG 2010 polyp surveillance guidelines and latest evidence. Results 406 patients were recruited from July to December 2017. 7 cancer and 126 polyp patients were BCSP colonoscopy diagnosed, giving an incidence of 4% and 65% respectively for London BCSP patients. Clinical data for the PTR-MS analysis using the H3O+and NO +precursor ions are presented in table 1. PTR data analysis so far indicates that there are discriminatory breath compounds between pathology groups, but analysis of possible influences of the bowel preparation regimen is ongoing. Conclusions Findings suggest that large scale breath testing is feasible within clinical practice. Whilst analysis of this preliminary dataset suggests the presence of discriminatory compounds between disease groups, analysis is ongoing. The true diagnostic accuracy of breath testing in this setting is expected to be revealed once all patients have been recruited to this study.