Cancer Risk for Patients Using Thiazolidinediones for Type 2 Diabetes: A Meta-Analysis

Objective. To clarify and quantify the effect of thiazolidinediones (TZDs; e. g., pioglitazone, rosiglitazone) on the risk of bladder cancer, other selected cancers, and overall cancer in patients with type 2 diabetes, we performed a systematic review and meta-analysis of observational studies. Methods. A PubMed/MEDLINE search was conducted for studies published in English up to June 30, 2012. Random-effect models were fitted to estimate summary relative risks (RR). Results. Seventeen studies satisfying inclusion criteria (3 case-control studies and 14 cohort studies) were considered. Use of TZDs was not associated to the risk of cancer overall(summary RR: 0.96; 95% confidence interval [CI]: 0.91-1.01). A modest excess risk of bladder cancer was reported in pioglitazone (RR: 1.20; 95% CI: 1.07-1.34 from six studies) but not in rosiglita-zone (RR: 1.08; 95% CI: 0.95-1.23 from three studies) users. The RRs of bladder cancer were higher for longer duration (RR: 1.42 for >2 years) and higher cumulative dose of pioglitazone (RR: 1.64 for >28,000 mg). Inverse relations were observed with colorectal cancer (RR: 0.93; 95% CI: 0.90-0.97 from six cohort studies) and liver cancer (RR: 0.65; 95% CI: 0.48-0.89 from four studies), whereas there was no association with pancreatic, lung, breast, and prostate cancers. Conclusions. Adequate evidence excludes an overall excess cancer risk in TZD users within a few years after starting treatment. However, there is a modest excess risk of bladder cancer, particularly with reference to pioglitazone. Assuming that this association is real, the potential implications on the risk-benefit analysis of TZD use should be evaluated. The Oncologist 2013;18:148-156