title: Metformin decreases lung cancer risk in diabetic patients in a dose-dependent manner.
abstract: OBJECTIVE
  Higher risk of lung cancer has been noted in patients with type 2 diabetes mellitus (DM). Some observational studies have shown a reduced risk of lung cancer in DM patients taking metformin, but a dose-response relationship has never been reported. The aim of this study is to exam the association between the dose of metformin and the incidence of lung cancer in a Chinese population.
  
  
  METHODS
  The dataset used for this nationwide population-based study is a cohort of 1 million subjects randomly sampled from individuals enrolled in the Taiwan National Health Insurance system. We enrolled all subjects with newly diagnosed type 2 DM between 1997 and 2007. Subjects with a diagnosis of neoplasm before DM diagnosis, those using metformin before DM diagnosis, those with polycystic ovary syndrome, and those with a DM diagnosis before their 15 years of age were excluded. The demographic data and duration, cumulative dose and intensity of metformin use were compared between patients developing lung cancer and those without lung cancer.
  
  
  RESULTS
  Totally, 47,356 subjects were identified. After adjusting for age, gender, and modified Charlson Comorbidity Index score, the utilization of metformin was an independent protecting factor, and the risk of developing lung cancer decreased progressively with either the higher cumulative dose or the higher intensity of metformin use.
  
  
  CONCLUSIONS
  This study revealed that the use of metformin decreased the risk of lung cancer in a dose-dependent manner in patients with type 2 DM. The chemo-preventive effect of metformin deserves further study.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Ming-Ju
authors.initials: MJ
authors.lastname: Tsai
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Internal Medicine, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Chih-Jen
authors.initials: CJ
authors.lastname: Yang
authors.affiliation: Administration Center, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Healthcare Administration and Medical Informatics, College of Health Science, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Kung
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Internal Medicine, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Chau-Chyun
authors.initials: CC
authors.lastname: Sheu
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Shen
authors.affiliation: Administration Center, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Pi-Yu
authors.initials: PY
authors.lastname: Chang
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Internal Medicine, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. Electronic address: shyang@kmu.edu.tw.
authors.forename: Ming-Shyan
authors.initials: MS
authors.lastname: Huang
authors.affiliation: Department of Healthcare Administration and Medical Informatics, College of Health Science, Kaohsiung Medical University, Kaohsiung, Taiwan. Electronic address: chiu@kmu.edu.tw.
authors.forename: Herng-Chia
authors.initials: HC
authors.lastname: Chiu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015897:Comorbidity; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D015994:Incidence; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology* / Q000401:mortality; D008297:Male; D008687:Metformin / Q000008:administration & dosage / Q000627:therapeutic use*; D008875:Middle Aged; D063868:Patient Outcome Assessment; D012306:Risk; D055815:Young Adult
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin
keywords: Chemoprevention; Diabetes mellitus; Lung cancer; Metformin; cancer; dose-dependence