Relationship Between Detection of Adenomas by Flexible Sigmoidoscopy and Interval Distal Colorectal Cancer

BACKGROUND & AIMS: Low rates of adenoma detection by colonoscopy have been associated with increased rates of interval colorectal cancer. We evaluated the relationship between the rate of adenoma detection by flexible sigmoidoscopy and interval distal colorectal cancer. METHODS: We analyzed data from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer screening trial, which used flexible sigmoidoscopy as a colorectal cancer screening modality (46,835 subjects; 66,711 examinations by 93 examiners). An adenoma detection rate was defined for each examiner as the number of examinations that identified adenomas (confirmed by pathology analysis) divided by the total number of screening examinations. Interval cancers were defined as cancers presumed detectable but not detected, which was based on the stage at diagnosis and the elapsed time from screening to diagnosis. RESULTS: The Prostate, Lung, Colorectal, and Ovarian Cancer study identified 32 interval distal cancers. The incidence of interval cancer for individuals screened by examiners in the lowest quartile of distal adenoma detection (2.0%-7.2%) was 9.0/10,000 examinations, whereas the incidence of interval cancers was lower among individuals whose examiners were in higher quartiles of adenoma detection, ranging from 3.0 to 5.4/10,000 examinations. The odds of interval distal cancer were significantly increased for patients of examiners in the lowest quartile of distal adenoma detection (<7.2%), with an adjusted odds ratio of 2.4 (95% confidence interval, 1.1 5.0; P = .02). CONCLUSIONS: Lower levels of adenoma detection by flexible sigmoidoscopy increase the risk for interval distal cancer. Detection of distal adenomas is a marker of the performance quality of flexible sigmoidoscopy. The parent study is registered under ClinicalTrials.gov, number NCT00002540.