nature publishing group COLON/SMALL BOWEL 663 © 2010 by the American College of Gastroenterology The American Journal of GASTROENTEROLOGY INTRODUCTION Colorectal cancer (CRC) continues to be the second most common cause of cancer-related deaths and premature mor- tality in North America (1). Although the recent reduction in the incidence of CRC in the United States has been attributed to screening with colonoscopy, the beneits of colonoscopy have not been shown in randomized controlled trials (2). Even though most colonoscopies are negative for colorectal neopla- sia, there are few large studies evaluating the incidence of CRC ater negative colonoscopy in usual clinical practice. In one of the irst population-based studies in this area, we had shown that the risk for CRC remains lower even beyond 10 years of the index negative colonoscopy (3). Although we reported age-standardized rates, our previous study has been criticized for including individuals of all ages at the index colonoscopy (4). A more recent study from Ontario suggested that the risk for proximal CRC ater a negative colonoscopy was the same as that in the general population in the irst 7 years ater the index colonoscopy (5). However, the risk of CRC ater a nega- tive colonoscopy has not been evaluated separately for men and women in published reports. It has been suggested that the colonoscopy completion rate may be lower among women (6). Predictors of Colorectal Cancer After Negative Colonoscopy: A Population-Based Study Harminder Singh, MD, MPH 1,2 , Zoann Nugent , PhD 2,3 , Salaheddin M. Mahmud , MD, PhD 2,3 , Alain A. Demers , PhD 2,3 and Charles N. Bernstein , MD 1 OBJECTIVES: A higher proportion of colorectal neoplasia among women occurs in the proximal colon, which might be more frequently missed by colonoscopy. There are no data on predictors of developing colorectal cancer (CRC) after a negative colonoscopy in usual clinical practice. We evaluated gender differences and predictors of CRC occurring after a negative colonoscopy. METHODS: All individuals 40 years or older with negative colonoscopy were identified from Manitoba’ s provincial physicians’ billing claims database. Individuals with less than 5 years of coverage by the provincial health plan, earlier CRC, inflammatory bowel disease, resective colorectal surgery, or lower gastrointestinal endoscopy were excluded. CRC risk after negative colonoscopy was compared to that in the general population by standardized incidence ratios. Cox regression analysis was performed to determine the independent predictors of CRC occurring after negative colonoscopy. RESULTS: A total of 45,985 individuals (18,606 men; 27,379 women) were followed up for 229,090 person-years. After a negative colonoscopy, men had a 40 – 50% lower risk of CRC diagnosis through most of the follow-up time. Risk among women was similar to that of women in the general population in the first 3 years and then was 40 – 50% lower. Older subject age and performance of index colonoscopy by non-gastroenterologists were independent predictors for early/missed CRC (cancers occurring within 3 years of negative colonoscopy). CONCLUSIONS: Women may have a higher rate of missed/early CRCs after negative colonoscopy. Predictors of missed/early CRCs after negative colonoscopy include older age and performance of index colonoscopy by a non-gastroenterologist. Am J Gastroenterol 2010; 105:663–673; doi:10.1038/ajg.2009.650; published online 10 November 2009 1 Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada; 2 Community Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada; 3 Department of Epidemiology and Cancer Registry, CancerCare Manitoba Winnipeg, Manitoba, Canada. Correspondence: Harminder Singh, MD, MPH, Section of Gastroenterology, University of Manitoba, 805-715 McDermot Avenue, Winnipeg, Manitoba, Canada R3E3P4. E-mail: singh@cc.umanitoba.ca Received 29 January 2009; accepted 2 October 2009 ORIGINAL CONTRIBUTIONS CME