Colorectal Cancer and Mortality Risk Among Older Adults With vs Without Adenoma on Prior Colonoscopy

Importance: Colorectal cancer (CRC) risk among older adults with prior adenoma is uncertain. Objective: To estimate cumulative CRC risks, non-CRC mortality, and all-cause mortality among adults 75 years of age or older with vs without adenoma at prior colonoscopy (in the latter of whom, guidelines recommend against repeat colonoscopy screening). Design, Setting, and Participants: Retrospective cohort study of older adults who underwent colonoscopy between January 1, 2006, and December 31, 2019, and prior to 75 years of age within the US Department of Veterans Affairs. Exposures: Colonoscopy with vs without adenoma prior to 75 years of age. Main Outcomes and Measures: Estimated cumulative incidence of CRC, CRC death, non-CRC death, and all-cause mortality for individuals with vs without adenoma at prior colonoscopy (incidence of CRC and CRC death were compared using the Gray test). For those with adenoma, incidence of CRC and non-CRC death were stratified based on 5 Veterans Affairs Frailty Index categories of increasing all-cause mortality risk (nonfrail, ≤0.10; prefrail, 0.11-0.20; mild frailty, 0.21-0.30; moderate frailty, 0.31-0.40; and severe frailty, >0.40). Results: Of 91 952 individuals (median age, 71 [IQR, 69-73] years at last colonoscopy; 98% male) who had undergone colonoscopy prior to 75 years of age, there were 25 538 (27.8%) with adenoma vs 66 414 (72.2%) without adenoma. At 10-year follow-up, the cumulative incidence of CRC was 1.1% (95% CI, 0.8%-1.3%) in those with adenoma vs 0.7% (95% CI, 0.5%-0.8%) in those without adenoma (Gray test P < .001). At 10-year follow-up, the cumulative incidence of CRC death was 0.5% (95% CI, 0.3%-0.7%) in those with adenoma vs 0.4% (95% CI, 0.3%-0.5%) in those without adenoma (Gray test P = .005). The cumulative incidence of non-CRC death ranged from 46.9% to 48.4% at 10 years. For those with adenoma, incidence of CRC was substantially exceeded by the cumulative incidence of non-CRC death at 10-year follow-up across all frailty levels (ranged from 34.2% among nonfrail individuals to 82.0% among severely frail individuals). Conclusions and Relevance: Adults 75 years of age or older with adenoma at prior colonoscopy were more likely to experience subsequent CRC and CRC death compared with those without adenoma, but cumulative risks were low and were far exceeded by competing risks for non-CRC death. Older adults may consider deprioritizing surveillance colonoscopy relative to other health concerns.