title: The effects of metformin on ovarian cancer: a systematic review.
abstract: OBJECTIVE
  The potential therapeutic effects of metformin on several cancers were reported. However, the evidence of the effects of metformin on ovarian cancer is still limited and inconclusive. This systematic review and meta-analysis study aim to summarize the existing evidence of the therapeutic effects of metformin on ovarian cancer.
  
  
  METHODS
  We performed systematic searches using electronic databases including PubMed and EMBASE until December 2012. Key words included "metformin" AND ("ovarian cancer" OR "ovary tumor"). All human studies assessing the effects of metformin on ovarian cancer were eligible for inclusion. All articles were reviewed independently by 2 authors with a standardized approach for the purpose of study, study design, patient characteristics, exposure, and outcomes. The data were pooled using a random-effects model.
  
  
  RESULTS
  Of 190 studies retrieved, only 3 observational studies and 1 report of 2 randomized controlled trials were included. Among those studies, 2 reported the effects of metformin on survival outcomes of ovarian cancer, whereas the other 2 reported the effects of metformin on ovarian cancer prevention. The findings of studies reporting the effects on survival outcomes indicated that metformin may prolong overall, disease-specific, and progression-free survival in ovarian cancer patients. The results of studies reporting the effects of metformin on ovarian cancer prevention were meta-analyzed. It indicated that metformin tended to decrease occurrence of ovarian cancer among diabetic patients with the pooled odds ratio of 0.57 (95% confidence interval, 0.16-1.99).
  
  
  CONCLUSIONS
  Our findings showed the potential therapeutic effects of metformin on survival outcomes of ovarian cancer and ovarian cancer prevention. However, most of the evidence was observational studies. There is a call for further well-conducted controlled clinical trials to confirm the effects of metformin on ovarian cancer survival and ovarian cancer prevention.
authors.affiliation: *Center of Pharmaceutical Outcomes Research, Department of Pharmacy Practice, Faculty of Pharmaceutical Sciences, Naresuan University, Phitsanulok, Thailand; †School of Population Health, University of Queensland, Brisbane, Australia; ‡School of Pharmacy, University of Wisconsin-Madison, Madison, WI; §Discipline of Pharmacy, Monash University Sunway Campus, Malaysia; and ∥Faculty of Medicine, Chulalongkorn University, Bangkok; ¶Faculty of Public Health, Naresuan University, Phitsanulok; and #School of Pharmaceutical Sciences, University of Phayao, Phayao, Thailand.
authors.forename: Piyemeth
authors.initials: P
authors.lastname: Dilokthornsakul
authors.forename: Nathorn
authors.initials: N
authors.lastname: Chaiyakunapruk
authors.forename: Wichai
authors.initials: W
authors.lastname: Termrungruanglert
authors.forename: Chayanin
authors.initials: C
authors.lastname: Pratoomsoot
authors.forename: Surasak
authors.initials: S
authors.lastname: Saokaew
authors.forename: Rosarin
authors.initials: R
authors.lastname: Sruamsiri
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008687:Metformin / Q000627:therapeutic use*; D010051:Ovarian Neoplasms / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology / Q000401:mortality; D016019:Survival Analysis; D016896:Treatment Outcome
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin