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.