Risk of Advanced Adenoma on the 2nd Surveillance Colonoscopy Based on Findings of the Index and 1st Surveillance Colonoscopies

Abstract

Purpose: To quantify the risk of advanced colorectal findings (defined as 1 or more advanced adenoma [AA]) on the 2nd surveillance colonoscopy (CY) as a function of the index CY and 1st surveillance CY. Methods: In this retrospective cohort study assembled from a single-site, community-based gastroenterology practice, we enrolled 965 consecutive subjects with no family history of colorectal cancer who had adenomatous polyps on index diagnostic or screening colonoscopy and who had two surveillance CYs. We recorded time interval and findings of the subsequent two surveillance CYs categorized by the most advanced finding: AA, non-advanced adenoma, nonadenoma/normal. The primary outcome was AA (size >=1cm, villous histology, or high-grade dysplasia) on the 3rd (i.e., 2nd surveillance CY) CY. For analysis, subjects were categorized as having or not having findings of AA on the index CY, 1st surveillance CY, and 2nd surveillance CY. Results: Mean age of the cohort was 57.8 +/- 9.8 years, 62% were men, and 36% had AA on index CY. Median intervals between the index and 1st surveillance CYs and between the 1st and 2nd surveillance CYs were 33.6 months and 42.8 months, respectively. Among 615 subjects with non-advanced index findings, 39 (6.3%; 95% CI, 4.6-8.6%) had AA on 1st surveillance CY. Within this subgroup of 615, 22 (3.8%; CI, 2.4-5.8%) of the 574 with normal / nonadvanced findings on the 1st surveillance CY had AA on the 2nd surveillance CY, as compared with 6 (15.4%; CI, 5.9-30.5%) of the remaining 39 who had AA on the 1st surveillance CY (relative risk [RR] = 4.03; CI, 1.51-9.01). Among 349 subjects with AA on index CY, 45 (12.9%; CI, 9.6-16.9%) had AA on 1st surveillance CY. Within this subgroup of 349, 19 (6.3%; CI, 3.8-9.6%) of the 304 with normal / non-advanced findings on the 1st surveillance CY had AA on the 2nd surveillance CY, as compared with 6 (13.3%; CI, 5.1-26.8%) of the remaining 45 who had AA on the 1st surveillance CY (RR = 2.13; CI, 0.78-5.25). If the 1st surveillance CY showed AA, then index findings added no information to subsequent risk of AA (13.3% if index AA vs. 15.4% if no index AA). If the 1st surveillance CY showed no AA, then the index findings added modestly to risk for AA on 2nd surveillance CY: 6.3% if index AA vs. 3.8% if no index AA (RR=1.64; CI, 0.91-2.95). Conclusion: Using a more restrictive definition of high-risk findings than previously published data (Robertson DJ, Ann Intern Med 2009), these results provide information about risk of AA on the 2nd sCY that may be useful for tailoring surveillance intervals following the 1st sCY. Specifically, among the subgroup with index non-advanced adenoma and 1st sCY with normal/nonadvanced findings, a longer surveillance interval may be appropriate.