title: Long-term metformin use reduces gastric cancer risk in type 2 diabetics without insulin treatment: a nationwide cohort study.
abstract: BACKGROUND
  Metformin use has been associated with a decreased incidence and mortality of various cancers.
  
  
  OBJECTIVE
  To evaluate the association between metformin use and gastric cancer.
  
  
  METHODS
  We randomly selected 100 000 type 2 diabetic patients from the 2004 Korean National Health Insurance claim database, and assessed gastric cancer incidence among 39 989 patients (aged 30-97 years) who were regularly treated with anti-diabetic drugs and followed-up from 2004 to 2010. In total, 26 690 patients had used metformin out of 32 978 diabetics who had not regularly used insulin (insulin non-users), and 5855 patients had used metformin out of 7011 regular insulin users.
  
  
  RESULTS
  Patients who used metformin showed a lower incidence of gastric cancer than those who did not use metformin, in insulin non-users (P = 0.047, log-rank test). However, in patients on regular insulin, there was no difference of gastric cancer incidence according to metformin use. In insulin non-users, the adjusted hazard ratio (AHR) for metformin use was 0.73 (95% confidential interval [CI], 0.53-1.01) with borderline statistical significance (P = 0.059). Duration of metformin use was associated with the reduction in gastric cancer risk (AHR, 0.88; 95% CI 0.81-0.96, P = 0.003), especially in patients who used metformin for more than 3 years (AHR, 0.57; 95% CI, 0.37-0.87; P = 0.009).
  
  
  CONCLUSIONS
  Metformin use >3 years in type 2 diabetics who do not use insulin is associated with a significantly reduced gastric cancer risk.
authors.affiliation: Center for Gastric Cancer, National Cancer Center, Goyang, Korea.
authors.forename: Y-I
authors.initials: YI
authors.lastname: Kim
authors.forename: S Y
authors.initials: SY
authors.lastname: Kim
authors.forename: S-J
authors.initials: SJ
authors.lastname: Cho
authors.forename: J-H
authors.initials: JH
authors.lastname: Park
authors.forename: I J
authors.initials: IJ
authors.lastname: Choi
authors.forename: Y J
authors.initials: YJ
authors.lastname: Lee
authors.forename: E K
authors.initials: EK
authors.lastname: Lee
authors.forename: M-C
authors.initials: MC
authors.lastname: Kook
authors.forename: C G
authors.initials: CG
authors.lastname: Kim
authors.forename: K W
authors.initials: KW
authors.lastname: Ryu
authors.forename: Y-W
authors.initials: YW
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D016208:Databases, Factual; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D015994:Incidence; D007328:Insulin / Q000627:therapeutic use; D008297:Male; D008687:Metformin / Q000008:administration & dosage / Q000627:therapeutic use*; D008875:Middle Aged; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012306:Risk; D013274:Stomach Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D013997:Time Factors
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D008687:Metformin