Colon Cancer Screening: A Win for Quality and Technology

David A. Johnson MD


May 27, 2014

Adenoma Detection Rate and Risk of Colorectal Cancer and Death

Corley DA, Jensen CD, Marks AR, et al
N Engl J Med. 2014;370:1298-1306

Study Summary

Although colonoscopy is recognized as the best test for colon cancer screening and prevention, considerable concern has arisen from reports of interval colorectal cancer (CRC) in patients who have had screening colonoscopy. More recent reports have identified the technique used to perform the colonoscopy as the variable that influences effectiveness with respect to CRC detection and prevention.

A CRC screening study from Poland demonstrated a highly significant relationship between the adenoma detection rate of colonoscopy and the risk for interval CRC. The study showed that if a patient developed interval CRC, it was 10-12 times more likely that the patient's examination had been conducted by a colonoscopist with a low adenoma detection rate (< 20%).[1] Similar findings were recently reported for performance characteristics in patients screened by flexible sigmoidoscopy.[2]

The current study by Corley and colleagues provides the best data to date on the importance of quality colonoscopy performance for CRC prevention. From a single health system, the investigators identified 264,972 colonoscopies in 223,842 patients, with 712 interval colorectal adenocarcinomas (8.2% of all colorectal cancers) and 927,523 person-years of follow-up for the analysis of interval cancer. All examinations were conducted by gastroenterologists, each of whom had performed more than 300 colonoscopies. Patients were excluded if CRC was detected within 6 months of the index examination or if the duration of available follow-up was less than 6 months.

Compared with the lowest quintile of colonoscopists' adenoma detection rate (7.1%-19.4%), the highest quintile (32.5%-52.5%) was associated with a 52% reduction in risk for CRC as well as a 62% reduction in CRC-related death. Furthermore, each 1% increase in the adenoma detection rate was associated with a 5% reduction in the risk for fatal interval CRC (hazard ratio, 0.95; 95% confidence interval, 0.94-0.97).


This report contains the strongest data to date on the importance of performing colonoscopy and optimizing its effectiveness for CRC prevention. Although the national quality metric (blended for men and women) is an adenoma detection rate of at least 20%, clearly this study demonstrated a relatively nominal advantage to the quintiles at this threshold (19%-24%; a 7% risk reduction). This threshold is extremely low, and this study provides the evidence as to why much higher adenoma detection rates are important.

Measurement of adenoma detection rates should be viewed as a current standard of care for colonoscopists and should be benchmarked across national standards. Longer withdrawal times, better definition of flat lesions when appropriate with chromoendoscopy or high magnification, high-quality adequate colon cleansing, and complete polyp resection are tools available with our technology and should be a priority for quality performance and optimal outcomes for CRC prevention.



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