title: Meta-analysis of alcohol consumption and risk of extrahepatic bile system cancer.
abstract: OBJECTIVE
  Alcohol consumption increases the risk of liver cancer. However, there is still controversy regarding alcohol consumption and the risk of extrahepatic bile system cancer (EBSC). We performed a meta-analysis to provide an overview of the relevant studies and gain more robust estimates of the relationship between alcohol consumption and risk of EBSC.
  
  
  METHODS
  Relevant studies published between January 1966 and October 2010 were identified by searching Medline, Embase and the Cochrane Library. Studies were selected using a priori defined criteria. The strength of the relationship between alcohol consumption and risk of EBSC was assessed by adjusted odds ratio (OR).
  
  
  RESULTS
  A total of 113 767 participants from 10 studies (nine case-control studies and one cohort study) were identified in this meta-analysis. The studies provided adjusted overall OR estimates for drinkers versus non-/low drinkers, leading to a pooled adjusted OR of 0.82 (95% confidence interval [CI] = 0.72-0.94, P for heterogeneity = 0.194, I(2)  = 27.2%). The overall adjusted OR of hospital-based studies and population-based studies were 0.80 (95% CI = 0.65-0.99, P = 0.260) and 0.79 (95% CI = 0.64-0.98, P = 0.119), respectively. For the heavy drinkers, the adjusted OR significance increased to 1.58 (95% CI = 0.97-2.57, P for heterogeneity = 0.055, I(2)  = 65.4%), but it had no statistical significance.
  
  
  CONCLUSIONS
  There is evidence that moderate alcohol consumption lowers the risk of EBSC compared with non-/low alcohol consumption, but not heavy alcohol consumption. Further multicenter and better controlled studies are required to confirm these findings.
authors.affiliation: Department of Hepatobilliary Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong Province, China.
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Kan
authors.forename: Yu-Qi
authors.initials: YQ
authors.lastname: Huang
authors.forename: Yong-Fa
authors.initials: YF
authors.lastname: Tan
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou