Five-Year Risk of Colorectal Neoplasia After Negative Screening Colonoscopy

Abstract

Recommendation for a 10-year interval for screening colonoscopy in persons at average risk for colorectal cancer is based on retrospective case–control data. There are no data from prospective studies of sufficient size and duration. This retrospective study determined the incidence of adenomas among individuals with no adenomas on baseline screening colonoscopy who were rescreened at a 5-year follow-up. The participants were 50 years or older and had undergone first-time screening from 1995 to 2000. The incidence of the following categories were determined: a cancer; an advanced adenoma (a tubular adenoma ≥1 cm in diameter, a polyp with high-grade dysplasia, or a villous component of at least 25%); a tubular adenoma ≤1 cm in diameter, a hyperplastic polyp; or no polyp. Among the 2983 persons screened for the first time, 2436 (81.7%) had no adenomas on baseline screening colonoscopy. At a mean of 5.3 ± 1.3 years later, 1256 of those with no adenomas (51.6%) underwent follow-up colonoscopy. At the time of baseline screening, the mean age of the participants was 56.7 years; 544 (43.3%) were women (mean age 57.1 years) and 712 (56.7%) were men (mean age 56.4 years). Among the 1256 persons re-screened, there were no cancers [95% confidence interval (CI) for the detection rate, 0% to 0.24%]. One or more neoplastic polyps were identified in 201 persons (16.0%). A total of 19 advanced adenomas were identified in 16 persons (1.3%). No significant difference was found at baseline in the risk of an advanced adenoma among persons without polyps [1.1% (12 of 1057)] and those with hyperplastic polyps [2.0% (4 of 199); relative risk, 1.77; 95% CI, 0.61–5.14]. The risk of any adenoma or an advanced adenoma was higher in men than women (relative risk, 1.88; 95% CI, 1.42–2.51 and 3.31; 95% CI, 1.02–10.8, respectively). For 1 advanced adenoma to be detected among all 1256 persons with normal findings at baseline, 79 would need to be rescreened at 5 years. Among women, 182 would need to be rescreened, whereas among men, 55 would need to be rescreened. These findings are consistent with previous data and support a rescreening interval of 5-years or longer after a normal colonoscopic examination in persons of average risk for colorectal cancer. The risk of an advanced adenoma is lower in women than in men.