• early diagnosis
• diagnosis
• medical oncology

Over the last 15 years, there have been dramatic changes in colorectal cancer (CRC) screening guidelines by the US Preventive Services Task Force (USPSTF). In 2008, grade A USPSTF screening recommendations for CRC suggested adults aged 50–75 receive either a flexible sigmoidoscopy (FS), faecal occult blood test (FOBT) or colonoscopy.1 In 2016, the USPSTF expanded the screening recommendations to include faecal immunochemical tests (FITs) and blood-based cancer screening for methylated SEPT9 DNA,2 the latter of which is theorised to improve screening rates owing to its non-invasive nature and preference over stool testing.3 At the time, editorialists addressed the limited clinical utility of these modalities compared with conventional FOBT, notably the inferior predictive value and potential indication drift of serology tests.4 Since the addition of these more uncertain screening tests, the debate has centred on whether expanding options will improve outcomes by drawing more participants or whether additional options will lead to worse outcomes by diverting people towards less effective methods.

Most recently, in 2021, the USPSTF took the additional step of using a model to extrapolate the lower limit of recommended screening to 45 years of age.5 These panel decisions seem to be more liberal in their approach to cancer screening, but they may actually lead to unanticipated outcomes, and there is currently little reliable evidence to establish if these recommendations are beneficial. As a result, two critical issues arise1: What are the potential consequences of making national clinical care recommendations based on lower levels of evidence?2 Is it appropriate for age cut-offs to be lowered based on modelling?

The purpose of providing more screening options is ostensibly to increase the fraction of people …