Abstract
BACKGROUND AND AIMS: Limited data are available to investigate the impact of index adenoma size on the risk of metachronous advanced adenomas. Our goal was to examine the impact of having small (5-9 mm) versus diminutive (<5 mm) adenomas on the future risk of advanced adenomas within the categories for polyps <1 cm currently used in the United States: 1 to 2 and 3 or more tubular adenomas. METHODS: We included data from individuals participating in the statewide, population-based New Hampshire Colonoscopy Registry (NHCR). Groups were based on index findings: (1) 1 to 2 adenomas <5 mm (both diminutive), (2) 1 to 2 adenomas <1 cm (one or both small), (3) 3 to 10 adenomas <5 mm (all diminutive), (4) 3 to 10 adenomas <1 cm (one or more small), and (5) advanced adenomas (AA). AAs were defined as adenomas ≥1cm or those with villous elements or high-grade dysplasia or colorectal cancer (CRC). Outcomes were the absolute and adjusted risk of metachronous AAs. Covariates included age, sex, body mass index, family history of CRC, lifestyle factors, presence of serrated polyps, and time since the index examination. RESULTS: After adjusting for the covariates, we observed that having 1 to 2 adenomas with at least one 5 to 9 mm adenoma (adjusted odds ratio [AOR], 1.54; 95% confidence interval [CI], 1.12-2.11), 3 to 10 diminutive adenomas (AOR, 1.75; 95% CI, 1.03-2.95), 3 to 10 adenomas <1 cm (1 or more small) (AOR, 2.14; 95% CI, 1.39-3.29) or AAs (AOR, 2.77; 95% CI, 2.05-3.74) were associated with an increased risk for metachronous AA compared with having 1 to 2 diminutive adenomas. A further stratification of group 2 showed that those with exactly 2 small adenomas had an absolute risk of future AA of 7.6% (11/144) (95% CI, 4.3%-13.2%), higher than the absolute risk in the 1 to 2 diminutive polyp group, and similar to the risk for 3 to 10 adenomas of 8.2% (95% CI, 5.4-11.9). CONCLUSIONS: For individuals with 1 to 2 adenomas <1 cm, having at least 1 small adenoma increased the metachronous risk of AA compared with having only diminutive adenomas. Furthermore, the subset with 2 small adenomas had a risk of future AA similar to the risk for 3 to 10 adenomas. These data suggest that individuals with at least 1 small adenoma may be at higher risk for future AAs and thus require closer follow-up than those with only diminutive adenomas. These data may be valuable to guideline committees for the creation of future surveillance recommendations.