Understanding colorectal cancer risk for symptomatic patients in primary care: A cohort study utilising faecal immunochemical tests and blood results in England

Abstract

SummaryBackgroundA faecal immunochemical tests (FIT) cut‐off of ≥10 μg Hb/g faeces is now recommended in the UK as a gateway to urgent (suspected cancer) investigation for colorectal cancer (CRC), based on an expected CRC risk threshold of 3%.AimsTo quantify the risk of CRC at FIT cut‐offs by age, haemoglobin and platelet strata.MethodsA cohort study of a symptomatic CRC pathway based on primary care FIT tests in Nottingham, UK (November 2017–2021) with 1‐year follow‐up. Heat maps showed the cumulative 1‐year CRC risk using Kaplan–Meier estimates.ResultsIn total, 514 (1.5%) CRCs were diagnosed following 33,694 index FIT requests. Individuals with a FIT ≥ 10 μg Hb/g faeces had a >3% risk of CRC, except patients under the age of 40 years (CRC risk 1.45% [95% CI: 0.03%–2.86%]). Non‐anaemic patients with a FIT < 100 μg Hb/g faeces had a CRC risk of <3%, except those between the age of 70 and 85 years (5.26% 95% CI: 2.72%–7.73%). Using a ≥3% CRC threshold in patients <55 years calculated using FIT, age and anaemia might allow 160–220 colonoscopies per 10,000 FITs to be re‐purposed, at a cost of missing 1–2 CRCs.ConclusionsFIT alone with a single cut‐off is unlikely to be a panacea for optimising CRC diagnosis, as risk varies by FIT, age and anaemia when faecal haemoglobin levels are below 100 μg Hb/g. Tailored FIT cut‐offs for investigation on a CRC pathway could reduce the number of investigations needed at a 3% CRC risk threshold.