Population‐Based Cohort Study: Colorectal Cancer Risk Stratification in Symptomatic Patients Using the Faecal Immunochemical Test, Blood Results and Patient Characteristics in Wales

BACKGROUND: Wales has the highest rate of colorectal cancer (CRC) in the UK. National guidelines recommend using the faecal immunochemical test (FIT) in patients presenting with symptoms of bowel cancer. FIT ≥ 10 μgHb/g in symptomatic patients is presumed to indicate a > 3% risk of CRC. However, evidence from England and Scotland has found that the risk is lower in certain demographic groups. AIMS: To examine 1-year risk of CRC in Welsh patients with symptoms of suspected bowel cancer by demographics, iron deficiency anaemia (IDA), and FIT. METHODS: Cohort study of adults registered in the Welsh Longitudinal General Practice dataset with a FIT recorded from 01/01/2020-31/03/2024. Kaplan-Meier estimates were used to calculate 1-year cumulative risks of CRC. RESULTS: We included 166,863 patients with a FIT; 19.2% had a FIT ≥ 10 μgHb/g. Within 1 year, 2864 (1.72%) were diagnosed with CRC; 90.2% of which were following FIT ≥ 10μgHb/g. A FIT cut-off of ≥ 10 μgHb/g in isolation identified a > 3% risk of CRC across all age groups. In those with FIT ≥ 10μgHb/g, IDA resulted in an increase in predicted risk across all age groups. IDA aided stratification further in women < 50 years; risk of CRC was 6.45% (95% CI: 3.52-9.29) with a FIT ≥ 10 μgHb/g and IDA compared to 2.20% (95% CI: 1.57-2.83) without IDA. CONCLUSIONS: In Wales, the risk of CRC following FIT ≥ 10 μgHb/g is higher than observed in English and Scottish cohorts. Stratification by demographics and blood results identified those at highest risk, but this did not fully explain the higher baseline risk observed in comparison to other UK nations.