Background: Each year in the United Kingdom there are over 44,000 deaths related to gastrointestinal (gut) cancers that include oesophageal (food pipe), stomach, pancreas, liver and bowel cancers. These cancers are difficult to detect as the symptoms are similar to non-cancer conditions. The delay in suspecting cancer and referral to a camera test (endoscopy) or scans can lead to the growth of cancer. Even with urgent referral only 4 out of every 100 patients are found to have cancer. If diagnosed early, the majority of people can survive gastrointestinal cancer. However, as the disease progresses, the number of people who survive falls significantly. Early diagnosis is therefore key. The proposed solution is a simple breath test for patients with relevant symptoms. Breath testing is quick, acceptable and can be offered directly by a GP. The breath samples are analysed for small molecules called volatile organic compounds. These molecules provide early indicators of gastrointestinal cancer, to identify those who would benefit most from investigations. Picking up gastrointestinal cancers earlier will increase the chances of curing the disease.

Aims: breath molecules that are specific to gastrointestinal cancers have been previously identified. The aim is to confirm these molecules and examine the accuracy of the breath test. How to implement the test in primary care will also be studied. Design and

Methods: Breath testing will be performed on at least 8,000 patients referred by GPs on suspected gastrointestinal cancer pathways. Patients will be followed up to determine whether they have gastrointestinal cancer or not. The breath test will take place in national NHS hospitals before patients undergo camera tests or scans. The breath test involves them breathing out into a bag allowing the breath to be collected into special tubes. The breath samples in the tubes will be analysed in the local laboratory. Which molecules in patients' breath samples correctly identify cancer will be confirmed. The key members will be engaged with to implement the breath test in primary care and NHS and assess the affordability of the breath test. Patient and public involvement and engagement (PPIE): A diverse PPIE group of 6 members affected by gastrointestinal cancer have identified clear benefits to patients and GPs and provided ways to improve patient recruitment. Work was with charities and appointed a patient representative to the local committee to support dissemination. The results will be disseminated through scientific papers and reports, conference presentations, public-facing areas, social media and cancer charity newsletters.