Risk of subsequent advanced adenoma or CRC in patients with low-risk adenoma on baseline colonoscopy

Reference

Dube C, Yakubu M, McCurdy BR, et al. Risk of advanced adenoma, colorectal cancer, and colorectal cancer mortality in people with low-risk adenomas at baseline colonoscopy: a systematic review and meta-analysis. Am J Gastroenterol 2017;112(12):1790-1801.

Synopsis

The authors define low-risk adenoma as 1 or 2 tubular adenomas smaller than 10 mm, no high-grade dysplasia, and average risk for CRC. Current US guidelines recommend follow-up in 5 to 10 years with colonoscopy, while European guidelines recommend only fecal tests for blood as in the general population. This systematic review identified any study (including cohort, case-control, and clinical trials) reporting follow-up data at least 3 years after an index colonoscopy. Patients with a low-risk adenoma identified on baseline colonoscopy were compared with those who had a normal baseline colonoscopy in some studies, and with the general population in others. The comparisons with the general population risk healthy volunteer bias, as persons adherent to recommendations for colonoscopy are likely to have better health outcomes in general.The authors found 11 studies, 8 of which provided data for the quantitative meta-analysis. All studies for advanced adenoma used normal colonoscopy as the comparator, while for CRC 2 out of 3 studies used general population control patients, as did the only study of CRC mortality. The studies using normal colonoscopy as the comparator ranged in size from 480 to 4483 patients, while those comparing patients with low-risk adenoma to the general population included 4380 to 40,826 patients. The mean or median age of participants ranged from 52 and 69 years, and the studies were largely judged to be of moderate to high quality. The likelihood of advanced adenoma at 5-year follow-up was 3.3% in those with an initially normal colonoscopy and 4.9% in those who had a low-risk adenoma at initial colonoscopy (relative risk 1.55; 95% CI 1.24 - 1.94; I� = 0%). A single cohort study found rates of high-grade dysplasia or CRC in 0.7 per 1000 person-years in patients with an initially normal colonoscopy and 1.4 per 1000 person-years in those with low-risk adenoma at baseline, although confidence intervals are broad and statistical significance of the difference is not reported. Studies using general population comparators found lower rates of CRC and CRC mortality in patients with low-risk adenoma than in the general population, but keep in mind that healthy volunteer bias.