ColonSys: an AI-powered risk stratification tool for improving FIT-based bowel cancer screening diagnostic yield

**NEED:** The UK's Bowel Cancer Screening Programme (BCSP) has been revolutionised by improved diagnostic methodology, the Faecal Immunochemical Test (FIT). FIT is easy to undertake (only one sample required), and so screening participation has increased from 59.4% to 67.5% of eligible adults aged \>50 years.

Any participant exceeding a pre-determined FIT threshold value that is universally applied to all samples screened is referred for colonoscopy to identify any medically actionable cause of bleeding i.e., colorectal cancer (CRC) or a precancerous adenoma (polyp).

Coupled to increased sensitivity of FIT vs. traditional guaiac-based faecal haemoglobin (f-Hb) detection, the number of referrals to colonoscopy is rising.

There are recognised weaknesses with FIT; ~45% of participants undergoing colonoscopy have neither CRC nor adenomas.

More worryingly however is that interval cancers (cancers that are detected between FIT screening rounds) account for ~50% of diagnosed bowel cancers. The high proportion of interval cancers can be explained by the high positive f-Hb FIT threshold (120 µg/g in England: 80 µg/g in Scotland). Recent modelling suggests that the NHS England FIT threshold of 120 µg/g could mean over 52% of CRC and 75% of high-risk adenomas may be missed.

Bowel Cancer UK and leading clinicians have recommended that the FIT threshold should be lowered to 20 µg/g to facilitate earlier detection of CRC, but this could increase the number of colonoscopies being performed from 650,000 to as many as 1.5 million procedures annually.

Colonoscopy is a costly, invasive procedure (c.£550 per colonoscopy). Moreover, during the Covid-19 pandemic, there is additional impetus to reduce unnecessary procedures and staff/patient hospital interactions for infection control, whilst making the NHS more efficient by using critical resources more wisely.

There is thus a significant and pressing **unmet need** for improving the diagnostic yield from FIT and avoiding unnecessary colonoscopy.

**SOLUTION:** Advanced Expert Systems Ltd (AES) have joined clinical academics from the University of Dundee and University Hospitals Coventry & Warwickshire Midlands NHS Trust to develop an AI-based software platform 'ColonSys' to interpret FIT result in the context of other risk factors.

As a multivariate stratification model, ColonSys optimises clinical resources by risk, with a gradient from high-risk patients being fast-tracked for further investigation, to patients with no risk having their next FIT screen delayed.

ColonSys will make BCSPs more efficient, with only high-risk patients requiring colonoscopy.

**TIMELINESS:** Due to Covid-19, there is additional impetus to reduce unrequired hospital visits and improve NHS efficiency.