Risk and cause of interval colorectal cancer after colonoscopic polypectomy

Background: To investigate the cause and risk of interval colorectal cancer (ICC) in patients undergoing surveillance colonoscopy within 5 years after colonoscopic polypectomy. Patients and Methods: We retrospectively analyzed data (endoscopy, pathology, demography) of patients who received surveillance colonoscopy within 5 years after colonoscopic polypectomy. Results: Among 1,794 patients undergoing surveillance colonoscopy within 5 years after colonoscopic polypectomy, 14 suffered from ICC. The mean follow-up time was 2.67 years and the incidence density of ICC was 2.9 cases per 1,000 person-years. 50% of ICCs were found in patients in whom adenomas had been incompletely removed by endoscopic therapy, 36% were missed cancers, and 14% were new cancers. Age >60 years (OR 2.97, 95% CI 2.31-3.82) was significantly associated with interval cancer on the surveillance colonoscopy as were advanced adenoma (OR 1.28, 95% CI 1.01-1.62), the presence of villous (HR 1.38, 95% CI 1.03-1.85) and high-grade dysplasia (OR 1.61, 95% CI 1.07-2.42). Conclusions: Among patients undergoing surveillance colonoscopy within 5 years after polypectomy, the incidence density of ICC was 2.9 cases per 1,000 person-years. The majority of interval cancers originated from incomplete resection of advanced adenomas and missed cancers, which can be prevented by improving endoscopic techniques and selecting an appropriate follow-up time interval.