Screening colonoscopy versus sigmoidoscopy: implications of a negative examination for cancer prevention and racial disparities in average-risk patients - 16/10/14

Doi : 10.1016/j.gie.2014.03.015

Bechien U. Wu, MD, MPH ^1,^2,^⁎, George F. Longstreth, MD ^1,³, Eunis W. Ngor, MS ⁴
¹ Center for Digestive Health Research, Southern California Permanente Medical Group, Los Angeles, California, USA
² Division of Gastroenterology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California, USA
³ Division of Gastroenterology, Kaiser Permanente San Diego Medical Center, San Diego, California, USA
⁴ Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California, USA

^∗Reprint requests: Bechien U. Wu, MD, MPH, 1526 N. Edgemont Ave., Los Angeles, CA 90027.

Abstract

Background

Both colonoscopy and flexible sigmoidoscopy are accepted procedures for colorectal cancer (CRC) screening in the United States.

Objective

To compare risk of CRC after negative findings on screening colonoscopy versus sigmoidoscopy and to evaluate racial/ethnic disparities in postscreening CRC.

Design

Retrospective, comparative cohort study.

Setting

Integrated community-based health-care system.

Patients

Average-risk patients 50 to 75 years of age with negative findings on an initial endoscopic screening examination from January 2000 to December 2010.

Interventions

Colonoscopy versus sigmoidoscopy as the initial screening procedure.

Main Outcome Measurements

Incident cases of CRC identified via a prospective internal cancer registry, risk of CRC determined by Cox regression adjusted for age, sex, race/ethnicity, and comorbidity.

Results

The study cohort included 138,297 patients (42,938 patients with negative findings on colonoscopy and 95,359 with negative findings on sigmoidoscopy). The median age was 57.9 years (interquartile range 53.0-64.1 years). Women comprised 51.8% of the cohort with 42.2% non-Hispanic white patients, 24.1% Hispanic patients, 10.7% non-Hispanic black patients, 9.7% Asian patients, and 13.3% other/unknown. A total of 241 cases of CRC was detected during 553,543 person-years of follow-up. The adjusted hazard ratio (HR) of postscreening CRC was 0.42 (95% confidence interval [CI], 0.28-0.64; P < .0001) for colonoscopy versus sigmoidoscopy. Risk reduction was primarily among proximal tumors (adjusted HR 0.30; 95% CI, 0.16-0.57). Non-Hispanic black patients were at higher risk of postscreening CRC compared with non-Hispanic white patients (adjusted HR 1.71; 95% CI, 1.20-2.42); however, this disparity was noted only in the sigmoidoscopy cohort.

Limitations

Retrospective study with potential selection bias and residual confounding.

Conclusions

Negative screening colonoscopy was associated with decreased incidence of subsequent CRC and a decrease in disparities compared with negative sigmoidoscopy findings in this large, community-based setting.

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Abbreviations : CI, CRC, HR, KPSC