Beyond the scope: an update on colon cancer screening tests

Colorectal cancer (CRC) is common and rising among persons under age 50, but screening uptake is sub-optimal, particularly in 45-49 year-olds. Death from CRC can be prevented through detection and removal of advanced precancerous colorectal lesions (APLS) or detection of CRC at an early stage. In this review, we cover average-risk CRC screening options and present a framework for test selection in different clinical settings.

The optimal CRC screening test should be highly sensitive for APLs and early stage CRC, easy to access, affordable to patient and payers, and appropriate for screening settings. Organized screening is administered systematically on the population-level, while opportunistic screening relies on individual provider-patient shared decision making. In addition to established options such as fecal immunochemical testing, multitarget stool DNA testing, and colonoscopy, novel options include stool-based RNA testing, next-generation stool-based DNA testing, and blood-based DNA testing. Although blood-based tests may be convenient, their low sensitivity for APLs can unintentionally lead to negative consequences for CRC prevention.

Uptake, cost, and efficacy of established and novel CRC screening tests influence the modality of choice for specific screening settings. Colonoscopy and stool-based tests should generally be first-line for CRC screening.