Yield and Risk Factors for Advanced Colorectal Neoplasia and Long-term Outcomes in Veterans With 3 or More Nonadvanced Adenomas

Background and Aims: Until recently, guidelines recommended a 3-year surveillance colonoscopy for persons with 3 to 10 nonadvanced adenomas (NAA). In this study, we quantify yield for metachronous advanced neoplasia (AN); attempt to identify risk factors for AN; and measure colorectal cancer (CRC) incidence and mortality. Methods: We used natural language processing to screen an existing data set for Veterans with 3 to 10 NAA. We manually reviewed colonoscopy and pathology reports to verify baseline findings and determine results of subsequent colonoscopy (sCY). Baseline features were extracted from the electronic medical record (EMR) and a national data set, CRC incidence was obtained from the Veterans Affairs cancer registry, and CRC mortality from the National Death Index through September 30, 2017. CRC incidence and mortality were compared between Veterans who did versus did not have sCY. Results: Natural language processing identified 3673 Veterans who potentially had 3 to 10 NAA, of which 1672 were excluded after EMR review. In the analytical cohort of 2001 subjects, 1178 (59%) had sCY at a mean (SD) follow-up of 4.3 (2.2) years. The sCY group was younger (mean age: 61 vs. 67 y; P<0.01) and were less likely to have diabetes (27% vs. 31%; P=0.02) and congestive heart failure (4% vs. 9%; P<0.01). sCY showed AN in 182 subjects (15.5%). Baseline features were no different between those with versus without metachronous AN. Subjects with sCY had a greater CRC incidence (n=7 vs. n=0; P=0.046), but there was no difference in CRC mortality (0 for both subgroups). Conclusions: Among patients with 3 to 10 NAA on index colonoscopy who underwent sCY, AN was present in 15.5% at mean follow-up of 4.3 years. No risk factors for AN were identified. CRC incidence, but not CRC mortality, was higher among those with sCY.