Post-Colonoscopy Colorectal Cancer in Fecal Immunochemical Test-Positive Individuals: Prevalence, Predictors, and Root-Cause Analysis in a Nationwide Cohort

Objectives: Post-colonoscopy colorectal cancer (PCCRC) represents an important real-world colonoscopy quality indicator. Using a national database, we evaluated predictors of PCCRC in fecal immunochemical test (FIT)-positive individuals, determined the PCCRC 3-year rate (PCCRC-3y), and performed a root cause analysis (RCA). Methods: This retrospective cohort study evaluated FIT-positive patients who underwent colonoscopy from January 2015 to July 2022. Data was collected from the Veterans Affairs (VA) national database. PCCRC was defined as CRC detected ≥6 months after colonoscopy. CRC was identified using SNOMED codes and the VA Cancer Registry. The World Endoscopy Organization methodology was used to perform the RCA and calculate the PCCRC-3y rate. Results: We identified 132 PCCRCs among 52,167 FIT-positive individuals. The PCCRC-3y rate was 6.4% (95% CI, 5.0-7.7%). PCCRC locations were proximal colon (43.2%), distal colon (34.8%), and rectum (22%). Root causes were likely new CRC (17.4%), missed lesions with adequate (31.2%) or inadequate (9.8%) examination, incomplete polyp resection (22%), and detected but unresected lesions (19.7%). 16.7% of patients with PCCRC had poor bowel preparation on index colonoscopy. The cecal intubation rate was 88.6% and rectal retroflexion rate was 84.5%. In 14.4% of cases, recommended surveillance intervals did not adhere to established guidelines. Independent predictors of PCCRC were ages 70-79 (HR 7.86; 95% CI, 1.08-57.39), age ≥80 (HR 10.18; 95% CI, 1.06-97.98), tubulovillous adenoma (HR 3.98; 95% CI, 2.52-6.29), and adenoma with high-grade dysplasia (HR 10.15; 95% CI, 5.91-17.42). Conclusions: Among FIT-positive individuals, the PCCRC-3y rate was 6.4%, with missed lesions and incomplete resection as key contributors. These findings provide useful information on quality metrics in FIT-based CRC screening programs.