Risk of Metachronous Advanced Colorectal Neoplasia After Removal of Diminutive Versus Small Nonadvanced Adenomas: A Multicenter Study

Background Current postpolypectomy guidelines treat 1–9 mm nonadvanced adenomas (NAAs) as carrying the same level of risk for metachronous advanced colorectal neoplasia (ACRN). Aims To evaluate whether small (6–9 mm) NAAs are associated with a greater risk of metachronous ACRN than diminutive (1–5 mm) NAAs. Methods We retrospectively evaluated 10,060 index colonoscopies performed from July 2011 to June 2019. A total of 1369 patients aged ≥ 40 years with index NAAs and having follow-up examinations were categorized into 5 groups based on size and number of index findings: Group 1, ≤ 2 diminutive NAAs ( n = 655); Group 2, ≤ 2 small NAAs ( n = 529); Group 3, 3–4 diminutive NAAs ( n = 78); Group 4, 3–4 small NAAs ( n = 65); and Group 5, 5–10 NAAs ( n = 42). Size was classified based on the largest NAA. ACRN was defined as finding an advanced adenoma or colorectal cancer at follow-up. Results The absolute risk of metachronous ACRN increased from 7.2% in patients with all diminutive NAAs to 12.2% in patients with at least 1 small NAA ( P = 0.002). Patients in Group 2 (adjusted odds ratio [AOR] 1.89; 95% confidence interval [CI], 1.21–2.95), Group 3 (AOR 2.40; 95% CI 1.78–4.90), Group 4 (AOR 2.77; 95% CI 1.35–5.66), and Group 5 (AOR 3.71; 95% CI 1.65–8.37) were associated with an increased risk of metachronous ACRN compared with Group 1. Conclusions Patients with small NAAs have an increased risk of metachronous ACRN. Postpolypectomy guidelines should consider including risk stratification between small and diminutive adenomas.