Long-term cumulative incidence of metachronous advanced colorectal neoplasia after colonoscopy and a novel risk factor: a cohort study.

Abstract

Long-term cumulative incidence of and risk factors for metachronous advanced colorectal neoplasia, including both advanced colorectal adenoma (≥10 mm, or with villous or high-grade dysplasia) and colorectal cancer, are critical for surveillance strategies. The aim of this study was to determine the cumulative incidence of metachronous advanced colorectal neoplasia and its risk factors. A retrospective cohort study was conducted on 6720 consecutive individuals who underwent general health check-ups and colonoscopy. Colorectal adenomas at initial colonoscopy were categorized as low-risk (1-2 small [<10 mm] tubular adenomas) or high-risk adenoma (≥3 tubular adenomas of any size; at least one adenoma ≥10 mm; or villous adenoma or adenoma with high-grade dysplasia). Kaplan-Meier estimates and hazard ratio by Cox-proportional hazard regression were calculated. The cumulative incidence (95% confidence interval [CI]) of metachronous advanced colorectal neoplasia at 5 and 10 years was 5.7% [4.6-7.1], and 11% [8.9-14] in the low-risk adenoma group, and 10% [8.6-13], and 17% [14-21] in high-risk adenoma group, respectively. Adjusted hazard ratio [95% CI] of low-risk adenoma (vs. no colorectal adenoma), high-risk adenoma (vs. no colorectal adenoma), current smoking and positive fecal immunochemical test were 1.34 [1.04-1.74], 1.94 [1.48-2.55], 1.55 [1.2-2.02] and 1.69 [1.35-2.1], respectively. Adjusted hazard ratio [95% CI] of positive fecal immunochemical test was 1.88 [1.29-2.74] in those with normal colonoscopy. Both low-risk and high-risk adenomas confer substantial risk for metachronous advanced colorectal neoplasia at 10 years. Positive fecal immunochemical test was a significant risk factor for metachronous advanced colorectal neoplasia despite normal colonoscopy.