Risk of post-colonoscopy colorectal cancer due to incomplete adenoma resection: A nationwide, population-based cohort study.

Background: Most post-colonoscopy colorectal cancers (PC-CRCs) are thought to develop from missed or incompletely resected adenomas.

Aims: We aimed to assess the incidence rate of PC-CRC overall and per colorectal segment, as a proxy for PC-CRC due to incomplete adenoma resection, and to identify adenoma characteristics associated with these PC-CRCs.

Methods: We performed a nationwide, population-based cohort study, including all patients with a first colorectal adenoma between 2000-2010 in the Dutch Pathology Registry (PALGA). Outcomes were the incidence rate of PC-CRC overall and of PC-CRC in the same colorectal segment, occurring between six months and five years after adenoma resection. A multivariable Cox proportional hazard analysis was performed to identify factors associated with PC-CRCs in the same segment.

Results: We included 107,744 patients (mean age 63.4 years; 53.6% male). PC-CRC was detected in 1031 patients (0.96%) with an incidence rate of 1.88 per 1000 person years. PC-CRC in the same segment was found in 323 of 133,519 adenomas (0.24%) with an incidence rate of 0.56 per 1000 years of follow-up. High-grade dysplasia (hazard ratio (HR) 2.54, 95% confidence interval (CI) 1.99-3.25) and both villous (HR 2.63, 95% CI 1.79-3.87) and tubulovillous histology (HR 1.80, 95% CI 1.43-2.27) were risk factors for PC-CRC in the same segment.

Conclusions: Approximately one-third of PC-CRCs are found in the same colorectal segment after adenoma resection and could therefore be a consequence of incomplete adenoma resection, occurring in one in 400 adenomas. The risk of PC-CRC in the same segment is increased in adenomas with high-grade dysplasia or (tubulo)villous histology.