Abstract
BACKGROUND & AIMS: The term "advanced adenoma" (AA) includes adenomas ≥1 cm, ones with villous histology or high-grade dysplasia (HGD), or polyps that may be heterogeneous for metachronous advanced neoplasia (AN) risk (AA and adenocarcinoma). We compared risk in individuals with 10- to 19-mm tubular adenomas (TAs) vs those with HGD, villous histology, and TAs ≥20 mm (modified AAs). METHODS: We used the New Hampshire Colonoscopy Registry to identify individuals having index colonoscopies and follow-up exams 12 months or longer. Outcomes were metachronous AN and subsequent colorectal cancer (CRC). Using Poisson loglinear and Cox proportional hazards models, we compared adjusted metachronous risk of AA and CRC between the 2 AA subgroups and those with lesser findings. RESULTS: There were 35,941 adults stratified by index findings: Group 1: no adenomas (n = 20,857); Group 2: 1 to 2 small (<1 cm) TAs (n = 9927); Group 3: 3 to 10 small (<1 cm) TAs (n = 2124); Group 4: 10- to 19-mm TAs (n = 1492), and the modified AA group (Group 5) (n = 1541). Compared with Groups 1 to 3, Group 4 (rate ratio [RR], 3.67; 95% confidence interval [CI], 2.99-4.50) and Group 5 (RR, 4.69; 95% CI, 3.82-5.77) had higher adjusted AN risk, with overlapping 95% CIs. However, when using the modified AA definition as an outcome, we observed that the modified AA group had a statistically significantly higher risk for metachronous modified AA than the large (10-19 mm) TA group (RR, 1.52; 95% CI, 1.04-2.22). Compared with the low-risk groups (Groups 1-3), Group 4 (hazard ratio [HR], 2.44; 95% CI, 1.34-4.44) and Group 5 (HR, 3.52; 95% CI, 1.98-6.25) had higher HRs for CRC with overlapping CIs. CONCLUSIONS: The modified AA groups had a statistically higher risk of a modified AN outcome and a numerically higher CRC risk than the 10- to 19-mm TA group. Future studies should validate these findings and extend them by examining differences in metachronous risk within the 10- to 19-mm TA group.