title: Risk factors for metachronous colorectal cancer or polyp: A systematic review and meta-analysis.
abstract: OBJECTIVE
  We conducted a systematic review and meta-analysis to identify personal, lifestyle, and tumor-related risk factors for metachronous colorectal cancer (CRC) and polyp.
  
  
  METHODS
  Relevant studies were identified by searching MEDLINE, Web of Science and Cochrane Central Register through 15 May 2016. Estimates for associations were summarized using random effects models.
  
  
  RESULTS
  Fifty-five studies were included in the review. For individuals who had a CRC resection, having a synchronous polyp was a risk factor for metachronous CRC or polyp (relative risk [RR], 2.04; 95% confidence interval [CI], 1.48-2.82) and having a synchronous CRC (RR, 1.90; 95% CI, 1.25-2.91) and proximally located CRC (RR, 2.12; 95% CI, 1.24-3.64) were risk factors for metachronous CRC. For individuals who had a polypectomy, larger size (RR, 4.26; 95% CI, 2.11-8.57) or severe dysplasia of the initial polyp (RR, 5.15; 95% CI, 2.02-13.14), and having a synchronous polyp (RR, 2.52; 95% CI, 1.35-4.73) were risk factors for metachronous CRC; and a family history of CRC (RR, 1.90; 95% CI, 1.26-2.87), having a synchronous polyp (RR, 2.47; 95% CI, 1.74-3.50) and a larger size (RR, 1.49; 95% CI, 1.03-2.15) and proximal location of the initial polyp (RR, 1.20; 95% CI, 1.02-1.40) were risk factors for metachronous polyp. Meta-regression showed duration of follow-up was not a source of heterogeneity for most associations. There was no evidence that lifestyle factors were associated with metachronous CRC or polyp risk.
  
  
  CONCLUSIONS
  A comprehensive list of risk factors identified for metachronous CRC or polyp may have important clinical implications.
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Victoria, Australia.|Cancer Epidemiology Centre, Cancer Council Victoria, Melbourne, Victoria, Australia.
authors.forename: Harindra
authors.initials: H
authors.lastname: Jayasekara
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Jeanette C
authors.initials: JC
authors.lastname: Reece
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Victoria, Australia.|Colorectal Oncogenomics Group, Genetic Epidemiology Laboratory, Department of Pathology, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Daniel D
authors.identifier: http://orcid.org/0000-0003-2225-6675
authors.initials: DD
authors.lastname: Buchanan
authors.affiliation: Department of Medicine, University of Colorado School of Medicine, Denver, Colorado, USA.
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Ahnen
authors.affiliation: New Zealand Familial Gastrointestinal Cancer Service, Auckland, New Zealand.
authors.forename: Susan
authors.initials: S
authors.lastname: Parry
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Jenkins
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Aung Ko
authors.identifier: http://orcid.org/0000-0002-2794-5261
authors.initials: AK
authors.lastname: Win
mesh_terms: D000368:Aged; D003111:Colonic Polyps / Q000150:complications* / Q000473:pathology; D015179:Colorectal Neoplasms / Q000150:complications*; D016206:Databases, Bibliographic; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D012307:Risk Factors
keywords: colorectal cancer; metachronous; risk factors; systematic review