Risk Factors for Metachronous Colorectal Cancer or Advanced Adenomas After Endoscopic Resection of High-risk Adenomas

BACKGROUND & AIMS: Among the characteristics of high-risk adenomas (HRAs), some may predict a higher risk of metachronous advanced lesions. Our aim was to assess which HRA characteristics are associ-ated with high risk of metachronous colorectal cancer (CRC) or advanced adenomas (AAs).METHODS: We systematically searched Pubmed, EMBASE, and Cochrane for cohort studies and clinical trials of CRC or AA incidence at surveillance stratified by baseline lesion size, histology, and multiplicity. We calculated pooled relative risks (RRs) using a random-effects model. Hetero-geneity was assessed with the I2 statistic.RESULTS: Fifty-five studies were included, with 936,540 patients with mean follow-up 5.4 - 2.9 years. CRC incidence per 1000 person-years was 2.6 (2.1-3.0) for adenomas >20 mm, 2.7 (2.2-3.2) for high-grade dysplasia (HGD), 2.0 (1.8-2.3) for villous component, 0.8 (0.1-1.4) for >5 adenomas, 1.0 (0.7-1.2) for >3 adenomas. Metachronous CRC risk was higher in adenomas >20 mm vs 10 to 19 mm (RR, 2.08; 95% confidence interval [CI], 1.20-3.61), HGD vs low-grade dysplasia (RR, 2.89; 95% CI, 1.88-4.44), villous vs tubular (RR, 1.75; 95% CI, 1.33-2.31). No significant differences in CRC risk were found in Z3 adenomas vs 1 to 2 (RR, 1.24; 95% CI, 0.84-1.83), nor in Z5 adenomas vs 3 to 4 (RR, 0.79; 95% CI, 0.30-2.11). Compared with normal colonoscopy, RR for CRC risk was 2.61(95% CI, 2.06-3.32) for Z10mm, 6.62 (95% CI, 4.60-9.52) for HGD, 3.58 (95% CI, 2.24-5.73) for villous component, and 2.03 (95% CI, 1.40-2.94) for Z3 adenomas. Similar trends were seen for metachronous AAs.CONCLUSION: Metachronous CRC risk is highest in patients with baseline adenomas with Z20 mm or HGD. Multiplicity does not seem to be associated with substantially higher CRC risk in the near term.