title: Use of thiazolidinediones and the risk of bladder cancer among people with type 2 diabetes: a meta-analysis.
abstract: BACKGROUND
  Patients with type 2 diabetes have a 40% increased risk of bladder cancer. Thiazolidinediones, especially pioglitazone, may increase the risk. We conducted a systematic review and meta-analysis to evaluate the risk of bladder cancer among adults with type 2 diabetes taking thiazolidinediones.
  
  
  METHODS
  We searched key biomedical databases (including MEDLINE, Embase and Scopus) and sources of grey literature from inception through March 2012 for published and unpublished studies, without language restrictions. We included randomized controlled trials (RCTs), cohort studies and case-control studies that reported incident bladder cancer among people with type 2 diabetes who ever (v. never) were exposed to pioglitazone (main outcome), rosiglitazone or any thiazolidinedione.
  
  
  RESULTS
  Of the 1787 studies identified, we selected 4 RCTs, 5 cohort studies and 1 case-control study. The total number of patients was 2,657,365, of whom 3643 had newly diagnosed bladder cancer, for an overall incidence of 53.1 per 100,000 person-years. The one RCT that reported on pioglitazone use found no significant association with bladder cancer (risk ratio [RR] 2.36, 95% confidence interval [CI] 0.91-6.13). The cohort studies of thiazolidinediones (pooled RR 1.15, 95% CI 1.04-1.26; I(2) = 0%) and of pioglitazone specifically (pooled RR 1.22, 95% CI 1.07-1.39; I(2) = 0%) showed significant associations with bladder cancer. No significant association with bladder cancer was observed in the two RCTs that evaluated rosiglitazone use (pooled RR 0.87, 95% CI 0.34-2.23; I(2) = 0%).
  
  
  CONCLUSIONS
  The limited evidence available supports the hypothesis that thiazolidinediones, particularly pioglitazone, are associated with an increased risk of bladder cancer among adults with type 2 diabetes.
authors: Department of Public Health Sciences, University of Alberta, Edmonton, Alta.
authors: Isabelle N
authors: IN
authors: Colmers
authors: Samantha L
authors: SL
authors: Bowker
authors: Sumit R
authors: SR
authors: Majumdar
authors: Jeffrey A
authors: JA
authors: Johnson
mesh_terms: D000328:Adult; D015331:Cohort Studies; D015897:Comorbidity; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D000077205:Pioglitazone; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000009:adverse effects* / Q000627:therapeutic use; D001749:Urinary Bladder Neoplasms / Q000453:epidemiology*
chemical_list: D045162:Thiazolidinediones; D000077154:Rosiglitazone; D000077205:Pioglitazone