title: Effect of metformin on cancer risk and treatment outcome of prostate cancer: a meta-analysis of epidemiological observational studies.
abstract: BACKGROUND
  Laboratory studies have shown the anti-tumor effect of metformin on prostate cancer. However, recent epidemiological studies have yielded inconclusive results.
  
  
  METHODS
  We searched PubMed database from the inception to May 30 2014 for studies which assessed the effect of metformin use on cancer risk of prostate cancer, biochemical recurrence (BCR) and all-cause mortality of patients with prostate cancer. The pooled results and 95% confidence intervals (CIs) were estimated by random-effect model.
  
  
  RESULTS
  Twenty-one studies were eligible according to the inclusion criteria. Based on the pooled results of available observational studies, metformin use was significantly associated with a decreased cancer risk (14 datasets, 963991 male subjects, odds ratio: 0.91, 95% CI: 0.85-0.97) and BCR (6 datasets, 2953 patients, hazard ratio: 0.81, 95% CI: 0.68-0.98) of prostate cancer. However, the association of metformin use with all-cause mortality of patients with prostate cancer was not significant (5 datasets, 9241 patients, hazard ratio: 0.86, 95% CI: 0.64-1.14).
  
  
  CONCLUSIONS
  Results suggest that metformin use appears to be associated with a significant reduction in the cancer risk and BCR of prostate cancer, but not in all-cause mortality of patients with prostate cancer.
authors.affiliation: Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, the Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, P. R. China.
authors.forename: Hongliang
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, the Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, P. R. China.
authors.forename: Li
authors.initials: L
authors.lastname: Yin
authors.affiliation: Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, the Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, P. R. China.
authors.forename: Xuesong
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, the Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, P. R. China.
authors.forename: Xiujin
authors.initials: X
authors.lastname: Sun
authors.affiliation: Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, the Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, P. R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, the Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, P. R. China.
authors.forename: Hao
authors.initials: H
authors.lastname: Tian
authors.affiliation: Department of Radiation Oncology, Peking University First Hospital, Peking University, Beijing, P. R. China.
authors.forename: Xianshu
authors.initials: X
authors.lastname: Gao
authors.affiliation: Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research, the Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, P. R. China.
authors.forename: Xia
authors.initials: X
authors.lastname: He
mesh_terms: D006801:Humans; D008297:Male; D008687:Metformin / Q000627:therapeutic use*; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000453:epidemiology* / Q000401:mortality; D017594:Publication Bias; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D008687:Metformin