A Pilot Study Profiling Volatile Organic Compounds (VOCs) in the Breath of Patients with CRC Using Proton Transfer Mass Spectrometry Harrypal Panesar (Presenter) Imperial College London Presenter Bio: I am a final year medical student at the University of Liverpool. Recently, I completed an intercalation year at Imperial College London which was largely research based. At Imperial I undertook a project in the field of Metabolomics, specifically breath testing in colorectal cancer. My interests are in the field of surgery and using Metabolomics to enhance current practice.

Authors: Harrypal Panesar
Imperial College London

We initially asked the question: Is it possible to distinguish between health patients and those with colorectal cancer (CRC) using their breath profiles? Previous research has suggested differences in VOC profile between health and CRC patients using Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). However, we employed a new technique, Proton Transfer Mass Spectrometry (PTR-MS), to measure the VOC profile in the breath of CRC and healthy patients. Analysing the breath profile of 17 patients with CRC and comparing them to normal colons, we describe a profile of breath VOCs that are significantly different between normal and CRC patients.

Introduction

Background: Colorectal cancer (CRC) is the second most common cause of cancer death in the UK. Previous studies have demonstrated the ability to use a non-invasive breath test to measure volatile organic compounds (VOCs) which can distinguish patients with CRC and healthy colons. Proton Transfer Mass Spectrometry (PTR-MS) is a new analytical technique allowing for real time quantification of volatile organic compounds (VOCs). PTR-MS allows the possibility for the development of a breath test which accurately distinguishes patients with CRC and health colons.

Aims: The primary aim of the study is to investigate the VOC profile in the breath of CRC patients using Proton Transfer Mass Spectrometry (PTR-MS).

Objectives: (i) To compare the VOC profile in CRC patients against matched patients with normal colons. (ii) To investigate potential influencing factors, focusing on bowel preparation.

Methods

Methods: (i) A total of 17 patients with CRC were collected and age, gender and ethnicity matched with 17 endoscopically normal patients collected in colonoscopy. All patients were administered bowel preparation, specifically Moviprep. (ii) Of the 17 cancer patients, 3 were targeted in pre-assessment clinic to obtain a second breath sample with no Moviprep. For each sample, 500ml of breath was collected in thermal desorption tubes at a flow rate of 200ml/min using a ReCIVA mask. All samples were analysed by PTR-MS using H3O+ and NO+ ionisations.

Results

Results: (i) It was demonstrated that 12 and 6 statistically significant different compounds were identified using H3O+ and NO+ ionisations respectively. ROC curves for NO+ display sensitivity and specificity of 78% and 86% respectively. (ii) No significant difference was found between paired patients pre- and post-bowel preparation.

Conclusions & Discussion

Conclusion: The results show the potential for PTR-MS to identify a profile of exhaled VOCs which can accurately distinguish between CRC and healthy states. Moviprep does not alter the cancer compounds. The results support the future development of an accurate, non-invasive breath test to diagnose CRC.

Key words: Proton Transfer Mass Spectrometry, colorectal cancer, volatile organic compound, breath test, Moviprep

With thanks to Professor George Hanna, Dr Georgia Woodfield, Dr Ilaria Belluomo, Dr Andrea Romano and Ms Annabelle Waller for all their help and support. Thank you also to all patients who participated in the study.