Stand-Alone FIT Screening Poor Predictor of CRC Risk

19/04/2023

The study covered in this summary was published on medrxiv.org as a preprint and has not yet been peer reviewed.

Key Takeaway

Age and anemia status should be incorporated into standard fecal immunochemical test (FIT) screening to better predict the risk of colorectal cancer (CRC) and the need for an urgent colonoscopy.

Why This Matters

The British National Institute for Health and Care Excellence and other groups use 10 micrograms of hemoglobin per gram (μg Hb/g) of feces on FIT screening as a trigger for urgent colonoscopy based on the assumption that it portends a 3% or higher risk for CRC.
The investigators found that the one-size-fits-all approach overestimates the risk for CRC for many patients, leading to unnecessary colonoscopies and wasted resources.
The authors also found that incorporating age and anemia status into FIT screening vastly improves risk prediction and recommend incorporating these factors into FIT screening to better identify patients who have a 3% or higher risk for CRC and require an urgent colonoscopy.

Study Design

The team reviewed 33,694 symptomatic patients who had FIT screening in Nottingham, United Kingdom, primary care clinics from 2017 to 2021.
They used electronic medical records to assess the incidence of CRC in the group 1 year after screening, breaking down the results by FIT levels, age, and anemia status.
FIT levels were assessed by the widely used OC-Sensor test from Eiken Chemical, Tokyo.

Key Results

The overall 1-year cumulative risk for CRC was 1.5%.
Nonanemic patients met the 3% risk threshold only if they had a FIT of 40 μg Hb/g feces or higher.
Anemic patients met the 3% threshold at a FIT of ≥ 20 μg Hb/g feces or higher.
Patients under age 40 years met the 3% risk threshold only if they had a FIT ≥ 100 μg Hb/g feces and were anemic.
Nonanemic patients over 70 years old met the 3% risk threshold only if they had a FIT > 40 μg Hb/g feces.
Overall, patients with a FIT test of 10-20 μg Hb/g feces had a CRC risk of 1.1%, well below the 3% threshold.

Limitations

Repeat screenings were not included in the analysis and follow up was short.

Disclosures

There was no external funding for the study, and the investigators report no relevant financial relationships.

This is a summary of a preprint research study, “Assessing empirical thresholds for investigation in people referred on a symptomatic colorectal cancer pathway: a cohort study utilising faecal immunochemical and blood tests in England,” led by Colin Crooks of the Nottingham Biomedical Research Centre in the United Kingdom, provided to you by Medscape. The study has not been peer reviewed. The full text can be found at medrxiv.org.

M. Alexander Otto is a physician assistant with a master’s degree in medical science and a journalism degree from Newhouse. He is an award-winning medical journalist who has worked for several major news outlets before joining Medscape and also an MIT Knight Science Journalism fellow. Email: [email protected].

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