title: Survival benefits of metformin for colorectal cancer patients with diabetes: a systematic review and meta-analysis.
abstract: BACKGROUND
  Several studies suggest that metformin has the potential effect of reducing cancer risk. However, its survival benefit in patients with colorectal cancer (CRC) and diabetes is unknown. The aim of our study is to address the effect of metformin on outcomes for CRC based on a systematic review and meta-analysis.
  
  
  RESULTS
  We searched EMBASE and MEDLINE databases from inception through August, 2013, using search terms related to metformin, diabetes, colorectal cancer, and prognostic outcome. The outcome measures were hazard ratios (HRs) with 95% CIs comparing CRC survival in diabetic patients using metformin and without using metformin. The primary end points were overall survival (OS) and CRC specific survival (CS). A total of six cohort studies including 2,461 patients met full eligibility criteria. The pooled HR favoring metformin users was 0.56 for OS (95% CI, 0.41 to 0.77) and 0.66 for CRC-specific survival (95% CI, 0.50 to 0.87). Thus metformin therapy reduced the risk of all cause of death by 44% and the risk of CRC specific death by 34% in CRC patients compared to those in non-users. However, evidence of heterogeneity and possible publication bias was noted for OS.
  
  
  CONCLUSIONS
  Patients with CRC and diabetes treated with metformin appear to have an improved survival outcome. Prospective study should be warranted to examine the association between metformin exposure intensity as well as some other confounding variables and survival outcome in diabetic CRC patients.
authors.affiliation: Department of Colorectal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Zu-Bing
authors.initials: ZB
authors.lastname: Mei
authors.affiliation: Department of Epidemiology, School of Public Health, Wuhan University, Wuhan, People's Republic of China.
authors.forename: Zhi-Jiang
authors.initials: ZJ
authors.lastname: Zhang
authors.affiliation: Department of Colorectal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Chen-Ying
authors.initials: CY
authors.lastname: Liu
authors.affiliation: Department of Colorectal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Colorectal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Ang
authors.initials: A
authors.lastname: Cui
authors.affiliation: Department of Colorectal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Zhong-Lin
authors.initials: ZL
authors.lastname: Liang
authors.affiliation: Department of Colorectal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Guang-Hui
authors.initials: GH
authors.lastname: Wang
authors.affiliation: Department of Colorectal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors.forename: Long
authors.initials: L
authors.lastname: Cui
mesh_terms: D015179:Colorectal Neoplasms / Q000150:complications* / Q000188:drug therapy* / Q000473:pathology; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000188:drug therapy*; D006801:Humans; D008687:Metformin / Q000627:therapeutic use*; D009367:Neoplasm Staging; D016016:Proportional Hazards Models; D017594:Publication Bias; D016019:Survival Analysis
chemical_list: D008687:Metformin