title: Association between metformin therapy and incidence, recurrence and mortality of prostate cancer: evidence from a meta-analysis.
abstract: OBJECTIVE
  Previous studies suggested that metformin is associated with decreased risk of cancer; however, results specifically addressing the potential association with prostate cancer were limited and contradictory. This study considers the association between metformin and the incidence, mortality and recurrence of prostate cancer by performing a meta-analysis of observational studies.
  
  
  METHODS
  Literatures published before January 2014 were searched by using databases of PubMed and Embase. Pooled relative risks (RRs) were determined using a random effects model to evaluate the strength of association between metformin therapy and risk of prostate cancer.
  
  
  RESULTS
  Thirteen studies involving a total of 334 532 participants were included in this meta-analysis. Compared with the control group, metformin therapy was associated with significantly decreased incidence of prostate cancer [RR = 0.88, 95% confidence interval (CI) [0.78, 0.99], p = 0.03, I(2)  = 74.7%]. However, metformin therapy was not associated with decreased all-cause mortality (RR = 1.07, 95% CI [0.86, 1.32], p = 0.55, I(2)  = 58.2%) or decreased recurrence of prostate cancer (RR = 0.90, 95% CI [0.75, 1.09], p = 0.27, I(2)  = 0.0%). No publication bias was detected (pBegg  = 0.55, pEgger  = 0.46).
  
  
  CONCLUSIONS
  The present study suggested that metformin therapy may decrease the incidence of prostate cancer but that there was no association between the treatment and all-cause mortality or recurrence. It is recommended that this finding should be considered carefully and confirmed with further studies.
authors.affiliation: School of Public Health and Management, Chongqing Medical University, Chongqing, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Deng
authors.affiliation: Department of Cardiovascular Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: School of Public Health and Management, Chongqing Medical University, Chongqing, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Tang
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Skrip
authors.affiliation: School of Public Health and Management, Chongqing Medical University, Chongqing, China.
authors.forename: Jingfu
authors.initials: J
authors.lastname: Qiu
authors.affiliation: School of Public Health and Management, Chongqing Medical University, Chongqing, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: School of Public Health and Management, Chongqing Medical University, Chongqing, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
mesh_terms: D000368:Aged; D016588:Anticarcinogenic Agents / Q000627:therapeutic use*; D048909:Diabetes Complications / Q000453:epidemiology / Q000401:mortality / Q000517:prevention & control*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000188:drug therapy*; D019317:Evidence-Based Medicine; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D015994:Incidence; D008297:Male; D008687:Metformin / Q000627:therapeutic use*; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000150:complications / Q000453:epidemiology / Q000401:mortality / Q000517:prevention & control; D064887:Observational Studies as Topic; D011471:Prostatic Neoplasms / Q000150:complications / Q000453:epidemiology / Q000401:mortality / Q000517:prevention & control*; D012306:Risk
chemical_list: D016588:Anticarcinogenic Agents; D007004:Hypoglycemic Agents; D008687:Metformin
keywords: meta analysis; metformin; prostate cancer