A positive faecal immunochemical test (FIT) for bowel cancer symptoms often leads to a colonoscopy, but for many patients the test is positive yet no cancer is found — and no one knows what happens to them next. This matters because a positive FIT detects blood in the stool, which can signal colorectal cancer, but it may also indicate other serious diseases. Evidence from screening programmes suggests a positive FIT is linked to higher rates of non-cancer deaths and illnesses such as cardiovascular, respiratory, and digestive disease. Yet no population-based studies have examined these outcomes in symptomatic patients — a gap the British Society of Gastroenterology has flagged as a key research priority. If this research succeeds, it will provide the first population-level evidence on what actually kills or sickens people after a positive symptomatic FIT. That knowledge could allow the NHS to offer targeted follow-up investigations beyond colonoscopy — for example, checking for heart or lung disease — rather than simply discharging patients. This would streamline diagnostic pathways, improve patient safety, and directly support the NHS Long Term Plan for faster, more efficient cancer diagnosis.
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Background: Colorectal (CRC) the 3rd most common cancer and the 2nd highest cause of cancer death in the UK(1, 2). National guidelines support the use of the faecal immunochemical test (FIT) in patients with symptoms suggestive of CRC. A positive test denotes the presence of faecal blood and the need for urgent investigation for CRC such as colonoscopy(3). However, there is now an enlarging population of symptomatic patients with positive FIT but no evidence of CRC and it is unknown whether these patients require further investigation(3). Evidence from CRC screening suggests that a positive FIT is associated with increased all-cause and non-CRC mortality and other cancers, cardiovascular, respiratory and digestive diseases(4, 5). Yet, there are no population-based studies assessing these associations in symptomatic cohorts(4). This knowledge gap is highlighted as key research priorities in the 2022 British Society of Gastroenterology (BSG) guidelines which call for urgent evaluation of outcomes following symptomatic FIT(6). In late 2023, the NHS revealed its 'Faster Diagnosis Framework' which outlined recommendations and goals for cancer pathways in line with its Long Term Plan for Cancer(7). This framework aims to increase the efficiency of cancer pathways. Improved understanding of diseases and causes of death other than CRC associated with symptomatic FIT will enable identification of those requiring investigation beyond colonoscopy. This could significantly enhance the utility of FIT, improve patient experience and streamline diagnostic pathways aligning with the NHS framework aims. Aims: This project aims to quantify both cause-specific mortality and disease rates in those undergoing symptomatic FIT and to use this information to develop a strategy to further enhance the use of symptomatic FIT Objectives: To measure all-cause and cause-specific mortality in those who have undergone symptomatic FIT compared to the general population who have not been tested, adjusting for the competing risk of death To determine the incidence rate and cumulative incidence of non-CRC cancers, cardiovascular, digestive and respiratory disease following symptomatic FIT, compared to the general population. To formulate an effective implementation strategy, in collaboration with stakeholders, to appropriately select patients undergoing symptomatic FIT who require further investigation for the non-CRC diseases they are at risk of. Design: Objectives 1 and 2 will be addressed through 3 cohort studies utilising routinely collected data from Nottingham, CPRD (England) and SAIL (Wales) inclusive of over half a million patients who have undergone a symptomatic FIT in comparison to the general population between 2019-present. The outcomes of objective 1 and 2 will be discussed with key stakeholders to formulate an appropriate strategy for further investigations in select FIT positive individuals. Anticipated impact and dissemination The results will be the first population-level evidence examining mortality in symptomatic FIT. Identifying causes of death, other cancers and diseases diagnosed will enable proposal of targeted investigation and improve safety-net advise when CRC has been excluded in FIT positive patients. Through engaging directly with stakeholders to formulate an actionable implementation plan, a strategy for further investigation will be developed which directly relates to the NHS Long Term Plan.
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