Emerging exposure-driven accelerated colorectal carcinogenesis: a model with implications for screening colonoscopy effectiveness.

U.S. Multi-Society Task Force (2017 guideline, revised by the 2022 focused update on age to start and stop): offer average-risk colorectal cancer screening to everyone aged 45-75. Screening at 45-49 is a weaker recommendation than at 50-75. Colonoscopy every 10 years and annual FIT are the Tier 1 cornerstones. Tier 2 alternatives are multi-target stool DNA every 3 years, CT colonography every 5 years, and flexible sigmoidoscopy every 5-10 years. Capsule colonoscopy every 5 years is Tier 3. Any abnormal non-colonoscopy test requires a diagnostic colonoscopy, and a stool test should not be offered to a patient who would decline follow-up colonoscopy. Patients who are up to date with negative prior screening, particularly a high-quality colonoscopy, may consider stopping at 75 or when life expectancy is under 10 years. Decisions at 76-85 are individualized by health and prior screening, and screening after 85 is not recommended. The American Cancer Society's May 2026 guideline agrees on the 45-75 range, no screening after 85, and colonoscopy as the preferred option. It adds the next-generation mt-sDNA test and the multitarget stool RNA test (ColoSense), both every 3 years, and it adds an FDA-approved blood-based cfDNA test (Shield) only for people who decline or do not complete visual or stool screening. ACS says a positive stool or blood test should be followed by colonoscopy, preferably within 6 months. The 2026 ASGE paper on follow-up after an abnormal stool test is an implementation review (navigation, tracking, direct-access colonoscopy), not a new screening guideline.