Segmental metachronous adenoma rate as a metric for monitoring incomplete resection in a colonoscopy screening program.

ABSTRACT

BACKGROUND AND AIMS: Polypectomy technique has been shown to vary among colonoscopists, and interval colorectal cancer may result from incomplete resection of an adenoma. Methods to monitor polypectomy quality and the size of polyps resected to monitor have not been well defined. The aim of this study was to compare the rate of metachronous adenoma attributable to incomplete resection in polyps 6 to 9 mm versus polyps 10 to 20 mm. METHODS: The segmental metachronous adenoma rate attributable to incomplete resection (SMAR-IR) was calculated by subtracting the rate of metachronous neoplasia (MN) in segments without adenoma from segments with adenoma. The primary outcome of the study was the SMAR-IR in polyps 6 to 9 mm and 10 to 20 mm found on index colonoscopy. RESULTS: Of 337 patients included in the analysis, 146 patients had a tubular adenoma (TA) 10 to 20 mm in size and 191 patients a TA 6 to 9 mm in size as the most advanced lesion. For cases in which an index 10- to 20-mm TA was resected, the SMAR in segments with adenoma was 21.0% and in segments without adenoma 9.6%, so the SMAR-IR was 11.4% (95% confidence interval, 4.5-18.3). For cases in which an index 6- to 9-mm TA was resected, the SMAR in segments with adenoma was 22.0% and in segments without adenoma 8.8%, so the SMAR-IR was 13.2% (95% confidence interval, 7.2-19.4). Among 6 colonoscopists, the SMAR-IR ranged between 7.0% and 15.5% for polyps 6 to 20 mm. CONCLUSIONS: MN rates in segments with a TA 10-20 mm and a TA 6-9 mm are higher than the MN rates in segments without index neoplasia. Incomplete resection of neoplasia appears to be a significant risk factor for MN in 6- to 9-mm lesions as well as larger ones.