title: Prevalence, risk factors, and outcomes of interval colorectal cancers: a systematic review and meta-analysis.
abstract: OBJECTIVE
  We performed meta-analysis to estimate pooled prevalence, risk factors, and outcomes of interval colorectal cancers (CRCs).
  
  
  METHODS
  Systematic literature search through October 2013, identified population-based studies, reporting prevalence of interval CRCs (CRCs diagnosed within 6-36 months of colonoscopy). We estimated the pooled prevalence, patient, endoscopist, and tumor-related risk factors, as well as outcomes of interval CRCs, as compared with detected CRCs (CRCs diagnosed at or within 6 months of colonoscopy).
  
  
  RESULTS
  Twelve studies reporting on 7,912 interval CRCs were included. Pooled prevalence of interval CRCs was 3.7% (95% confidence interval (CI)=2.8-4.9%). These cancers were 2.4 times more likely to arise in the proximal colon (6.5%; 95% CI=4.9-8.6%) as compared with distal colon (2.9%; 95% CI=2.0-4.2%). Patients with interval CRCs were older (age >65-70 years vs. <65-70 years: odds ratio (OR)=1.15; 95% CI=1.02-1.30), have more comorbidities (high Charlson comorbidity index: OR=2.00; 95% CI=1.77-2.27), and have diverticular disease (OR=4.25; 95% CI=2.58-7.00). There was a nonsignificant time trend of declining prevalence of interval CRCs from 4.8% in 1990s to 4.2% between 2000 and 2005 and 3.7% beyond 2005. Patients with interval CRCs were less likely to present at an advanced stage (OR=0.79; 95% CI=0.67-0.94), although there was no survival benefit. Considerable heterogeneity was observed in most of the analyses.
  
  
  CONCLUSIONS
  Based on meta-analysis, approximately 1 in 27 CRCs are interval CRCs, although the confidence in these estimates is low because of the heterogeneity among the studies. These are more likely to arise in the proximal colon and are diagnosed in older patients, patients with comorbidities or diverticular disease.
authors: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, USA.
authors: Siddharth
authors: S
authors: Singh
authors: Department of Medical Oncology, Mayo Clinic, Rochester, Minnesota, USA.
authors: Preet Paul
authors: PP
authors: Singh
authors: 1] Division of Preventive Medicine, Mayo Clinic, Rochester, USA [2] Knowledge Synthesis Program, Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery, Mayo Clinic, Rochester, Minnesota, USA.
authors: Mohammad Hassan
authors: MH
authors: Murad
authors: Section of Gastroenterology, University of Manitoba and Cancer Care Manitoba, Winnipeg, Manitoba, Canada.
authors: Harminder
authors: H
authors: Singh
authors: Division of Gastroenterology, Huntsman Cancer Institute and University of Utah, Salt Lake City, Utah, USA.
authors: N Jewel
authors: NJ
authors: Samadder
mesh_terms: D000367:Age Factors; D003106:Colon / Q000473:pathology; D003111:Colonic Polyps / Q000175:diagnosis / Q000601:surgery; D003113:Colonoscopy / Q000592:standards / Q000706:statistics & numerical data; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics / Q000473:pathology; D004241:Diverticulum, Colon / Q000453:epidemiology; D006801:Humans; D015995:Prevalence; D012307:Risk Factors; D015996:Survival Rate; D013997:Time Factors