title: Cholelithiasis and risk of pancreatic cancer: systematic review and meta-analysis of 21 observational studies.
abstract: OBJECTIVE
  To investigate the association between cholelithiasis and risk of pancreatic cancer (PaC).
  
  
  METHODS
  We identified eligible studies in MEDLINE and EMBASE up to August 1, 2013 and the reference lists of original studies and review articles on this topic. Summary relative risks (SRRs) with their 95 % confidence intervals (CIs) were calculated with a random-effects model.
  
  
  RESULTS
  Twenty-one studies (15 case-control studies, 6 cohort studies) met eligibility criteria. The current data suggest that cholelithiasis is associated with a 25 % excess risk of PaC (SRRs = 1.25, 95 % CI 1.10-1.41; test for heterogeneity p = 0.006, I (2) = 47.6 %). In subgroup analysis of timing of exposure, seven of eight studies in patients whose diagnosis of cholelithiasis made more than specified year (5, 3, 2, or 1 year) prior to cancer diagnosis showed no association for PaC, while all three studies in patients diagnosed less than specified year before cancer diagnosis showed a positive association. There was no publication bias in the present meta-analysis.
  
  
  CONCLUSIONS
  This meta-analysis supports the hypothesis that a history of cholelithiasis may significantly increase PaC risk, particularly in Asian countries. However, the positive association disappeared over time, suggesting that cholelithiasis may be the early symptoms of PaC.
authors.affiliation: Department of Hepatobiliary Surgery, Affiliated Cancer Hospital of Guangzhou Medical University, 78 Hengzhigang Road, Guangzhou, 510095, China.
authors.forename: Yuanfeng
authors.initials: Y
authors.lastname: Gong
authors.forename: Siying
authors.initials: S
authors.lastname: Li
authors.forename: Yunqiang
authors.initials: Y
authors.lastname: Tang
authors.forename: Cong
authors.initials: C
authors.lastname: Mai
authors.forename: Mingchen
authors.initials: M
authors.lastname: Ba
authors.forename: Peng
authors.initials: P
authors.lastname: Jiang
authors.forename: Hui
authors.initials: H
authors.lastname: Tang
mesh_terms: D001208:Asia / Q000453:epidemiology; D016022:Case-Control Studies; D002769:Cholelithiasis / Q000150:complications*; D015331:Cohort Studies; D006801:Humans; D010190:Pancreatic Neoplasms / Q000453:epidemiology* / Q000209:etiology; D018570:Risk Assessment; D012307:Risk Factors