Colonoscopy Adenoma Detection Rate Inversely Proportional to Risk of Interval Colorectal Cancer and Colorectal Cancer Mortality

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Douglas A. Corley, MD, PhD, and colleagues

Impact of Colorectal Cancer Screening

These findings support the validity of the adenoma detection rate as a quality measure of physicians’ performance of colonoscopy in community practice. Studies to determine whether improving the adenoma detection rate leads to improved outcomes are warranted.

—Douglas A. Corley, MD, PhD, and colleagues

In a study of health-care organization data reported in The New England Journal of Medicine, Douglas A. Corley, MD, PhD, of Kaiser Permanente, and colleagues assessed the relationship between proportion of colonoscopies performed by a gastroenterologist that detect an adenoma and risk of subsequent interval colorectal cancer and colorectal cancer mortality.1 They found that adenoma detection rate is inversely proportional to risk of interval cancer and death from colorectal cancer.

Adenoma detection rate has been recommended as a quality benchmark and recently has been proposed as a reportable quality measure by the Centers for Medicare & Medicaid Services. Currently, adenoma detection rates ≥ 15% in women and ≥ 25% in men are recommended as indicators of adequate colonoscopy quality. Data validating these thresholds are lacking.

Study Details

The study involved analysis of 314,872 colonoscopies performed by 136 gastroenterologists in an integrated health-care delivery organization (Kaiser Permanente Northern California, total of 17 medical centers). Patients in the organization were enrolled in Medicare, Medicaid, or a commercial insurance plan and were included in the study if they had undergone a colonoscopy between January 1, 1998, and December 31, 2010, were ≥ 50 years old at the time of colonoscopy, and had at least 6 months of subsequent follow-up. Gastroenterologists included in the study had to have completed ≥ 300 colonoscopic examinations and ≥ 75 screening examinations during the study period.

Patients were followed from the date of the colonoscopy to completion of 10 years of follow-up, diagnosis of colorectal adenocarcinoma, discontinuation of membership in the health-care organization, or the end of the follow-up period on December 31, 2010.

Associations between adenoma detection rate and the risk of colorectal cancer diagnosed 6 months to 10 years after colonoscopy and cancer-related death were examined. Cox regression analysis adjusted for patient demographic characteristics, indications for colonoscopy, and coexisting conditions were used to estimate attributable risks for interval colorectal cancer, advanced-stage interval cancer, and fatal interval cancer.

Colorectal Cancer in Study Population

Of all colonoscopies, 58% were for diagnosis, 24% were for surveillance, and 18% were for screening. Exclusion of 8,018 examinations that detected cancer within 6 months of colonoscopy and an additional 41,882 examinations occurring with < 6 months of follow-up left 264,972 colonoscopies among 223,842 patients and totals of 712 interval colorectal adenocarcinomas (8.2% of all colorectal cancers), 255 advanced-stage cancers, and 147 deaths from interval colorectal cancer included in the analysis.

The median interval between index examination and the diagnosis of interval cancer was 39 months. Among the 712 interval cancers detected, the indication for colonoscopy was diagnosis for 55% of cases, surveillance for 33%, and screening for 13%.

Adenoma Detection Rates and Subsequent Risk

The average number of colonoscopies performed by individual physicians was 2,150 (range = 355–6,005). Adenoma detection rates ranged from 7.4% to 52.5% (9.7%–60.5% in male patients and 3.9%–45.9% in female patients). There was a strong correlation between adenoma detection rates based on screening alone and those based only on diagnostic examination (r = 0.75, P < .001) or only on surveillance (r = 0.72, P < .001).

Adenoma detection rates per lowest (1st) to highest (5th) quintile were 16.56% (range = 7.35%–19.05%), 21.50% (19.06%–23.85%), 25.70% (23.86%–28.40%), 30.96% (28.41%–33.50%), and 38.86% (33.51%–52.51%).

Unadjusted risks of interval cancer per 10,000 person-years of follow-up according to lowest to highest quintiles of adenoma detection rate were 9.8, 8.6 (hazard ratio [HR] vs 1st quintile = 0.83, 95% confidence interval [CI] = 0.70–1.23), 8.0 (HR = 0.85, 95% CI = 0.68–1.06), 7.0 (HR = 0.70, 95% CI = 0.54–0.91), and 4.8 (HR = 0.52, 95% CI = 0.39–0.69).

On adjusted analysis, compared with patients with physicians in the 1st quintile, risk reductions in the 4th and 5th quintiles were significant for any adenocarcinoma (adjusted hazard ratio [HR] = 0.70, 95% confidence interval [CI] = 0.54–0.91, for 4th quintile; HR = 0.52, 95% CI = 0.39–0.69, for 5th quintile), advanced-stage colorectal cancer (HR = 0.48, 95% CI = 0.33–0.71; HR = 0.43, 95% CI = 0.29–0.64), and colorectal cancer death (HR = 0.51, 95% CI 0.33–0.81; HR = 0.38, 95% CI = 0.22–0.65). Each 1.0% increase in the adenoma detection rate was associated with a 3.0% decrease in the risk of cancer (HR = 0.97, 95% CI = 0.96–0.98) and a 5.0% decrease in the risk of fatal interval cancer (HR = 0.95, 95% CI = 0.94–0.97).

Risk Reduction by Gender and Cancer Location

The association between the adenoma detection rate and the risk of interval cancer was observed both in women (HR for 5th vs 1st quintile = 0.43, 95% CI = 0.28–0.66) and men (HR = 0.60, 95% CI = 0.42–0.88), with no significant interaction according to sex (P = .23).

There was an inverse association between adenoma detection rate and subsequent risk of cancer in the proximal colon (HR for 5th vs 1st quintile = 0.49, 95% CI = 0.35–0.69) and distal colon (HR = 0.55, 95% CI = 0.39–0.79) and for early cancer (HR = 0.40, 95% CI = 0.23–0.68) and delayed cancer (HR = 0.61, 95% CI = 0.39–0.96).

As noted by the investigators, the hazard ratio of 0.52 for interval colorectal cancer suggests that physicians who increase their adenoma detection rate from < 19% (lowest quintile) to 34% to 53% (highest quintile) might prevent 1 additional interval cancer over the next 10 years for every 213 colonoscopies performed.

The investigators concluded:

[I]n a large community-based US population across multiple medical centers, physicians’ adenoma detection rates were inversely related to the risk of interval colorectal cancer, including advanced-stage cancer and fatal interval colorectal cancer, among patients with up to 10 years of follow-up. This association was approximately linear across quintiles of adenoma detection rates in our population and was observed for male and female patients, cancers in the proximal and distal colon, and early and delayed interval cancers. These findings support the validity of the adenoma detection rate as a quality measure of physicians’ performance of colonoscopy in community practice. Studies to determine whether improving the adenoma detection rate leads to improved outcomes are warranted. ■

Disclosure: The study was funded by the Kaiser Permanente Community Benefit program and the National Cancer Institute. For full disclosures of the study authors, visit


1. Corley DA, Jensen CD, Marks AR, et al: Adenoma detection rate and risk of colorectal cancer and death. N Engl J Med 370:1298-1306, 2014.

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