BACKGROUND The proportion of screening colonoscopic examinations performed by a physician that detect one or more adenomas (the adenoma detection rate) is a recommended quality measure. However, little is known about the association between this rate and patients’ risks of a subsequent colorectal cancer (interval cancer) and death. METHODS Using data from an integrated health care delivery organization, we evaluated the associations between the adenoma detection rate and the risks of colorectal cancer diagnosed 6 months to 10 years after colonoscopy and of cancer-related death. With the use of Cox regression, our estimates of attributable risk were adjusted for the demographic characteristics of the patients, indications for colonoscopy, and coexisting conditions. RESULTS We evaluated 314,872 colonoscopies performed by 136 gastroenterologists; the adenoma detection rates ranged from 7.4 to 52.5%. During the follow-up period, we identified 712 interval colorectal adenocarcinomas, including 255 advanced-stage cancers, and 147 deaths from interval colorectal cancer. The unadjusted risks of interval cancer according to quintiles of adenoma detection rates, from lowest to highest, were 9.8, 8.6, 8.0, 7.0, and 4.8 cases per 10,000 person-years of follow-up, respectively. Among patients of physicians with adenoma detection rates in the highest quintile, as compared with patients of physicians with detection rates in the lowest quintile, the adjusted hazard ratio for any interval cancer was 0.52 (95% confidence interval [CI], 0.39 to 0.69), for advanced-stage interval cancer, 0.43 (95% CI, 0.29 to 0.64), and for fatal interval cancer, 0.38 (95% CI, 0.22 to 0.65). Each 1.0% increase in the adenoma detection rate was associated with a 3.0% decrease in the risk of cancer (hazard ratio, 0.97; 95% CI, 0.96 to 0.98). CONCLUSIONS The adenoma detection rate was inversely associated with the risks of interval colorectal cancer, advanced-stage interval cancer, and fatal interval cancer. (Funded by the Kaiser Permanente Community Benefit program and the National Cancer Institute.)

ObjectiveScreening colonoscopy's effectiveness in reducing colorectal cancer mortality risk in community populations is unclear, particularly for right-colon cancers, leading to recommendations against its use for screening in some countries. This study aimed to determine whether, among average-risk people, receipt of screening colonoscopy reduces the risk of dying from both right-colon and left-colon/rectal cancers.DesignWe conducted a nested case–control study with incidence-density matching in screening-eligible Kaiser Permanente members. Patients who were 55–90 years old on their colorectal cancer death date during 2006–2012 were matched on diagnosis (reference) date to controls on age, sex, health plan enrolment duration and geographical region. We excluded patients at increased colorectal cancer risk, or with prior colorectal cancer diagnosis or colectomy. The association between screening colonoscopy receipt in the 10-year period before the reference date and colorectal cancer death risk was evaluated while accounting for other screening exposures.ResultsWe analysed 1747 patients who died from colorectal cancer and 3460 colorectal cancer-free controls. Compared with no endoscopic screening, receipt of a screening colonoscopy was associated with a 67% reduction in the risk of death from any colorectal cancer (adjusted OR (aOR)=0.33, 95% CI 0.21 to 0.52). By cancer location, screening colonoscopy was associated with a 65% reduction in risk of death for right-colon cancers (aOR=0.35, CI 0.18 to 0.65) and a 75% reduction for left-colon/rectal cancers (aOR=0.25, CI 0.12 to 0.53).ConclusionsScreening colonoscopy was associated with a substantial and comparably decreased mortality risk for both right-sided and left-sided cancers within a large community-based population.

We observed a lower follow-up for screen-detected abnormalities among blacks when compared with whites but little difference in the yield of colorectal neoplasia. Health-care utilization may be playing more of a role in colorectal cancer racial disparity than biology.