The predictive value of small versus diminutive adenomas for subsequent advanced neoplasia

Patients with previous colorectal adenomas are at increased risk of colorectal cancer. Current guidelines for postpolypectomy surveillance intervals treat all tubular adenomas 1 to 9 mm in size with low-grade dysplasia as carrying the same level of risk. We evaluated whether 6 to 9 mm adenomas detected at colonoscopy are associated with greater risk of advanced neoplasia at follow-up compared with baseline 1 to 5 mm adenomas.

We retrospectively evaluated a colonoscopy database at a single U.S. academic center. Patients with baseline examinations demonstrating tubular adenomas 1 to 9 mm in size with low-grade dysplasia and no advanced adenomas were included. Follow-up colonoscopies were performed at least 200 days later and were assessed for incident advanced neoplasia (cancer, high-grade dysplasia, adenoma ≥10 mm in size, or villous elements).

There were 2477 qualifying baseline colonoscopies. The absolute risk of metachronous advanced neoplasia increased from 3.6% in patients with 1 to 5 mm adenomas to 6.9% in patients with at least 1 adenoma of 6 to 9 mm (P = .001). Patients with 5 or more adenomas 1 of which was at least 6 to 9 mm had the highest risk of advanced neoplasia at follow-up (10.4%, P = .006). When only screening colonoscopies were considered, all baseline groups (1-2 adenomas, 3-4 adenomas, ≥5 adenomas) with adenomas 6 to 9 mm in size had an increased risk for metachronous advanced neoplasia (odds ratio [OR], 4.07; 95% confidence interval [CI], 1.50-11.04; OR, 4.91; 95% CI, 1.44-16.75; OR, 4.71; 95% CI, 1.30-17.05, respectively).

Patients with baseline small (6-9 mm) adenomas have an increased risk of advanced lesions on follow-up compared with patients with only diminutive (1-5 mm) adenomas. Postpolypectomy guidelines should consider risk stratification based on small versus diminutive adenomas.