People with type 2 diabetes are at increased risk of bladder cancer. Pioglitazone is said to increase it further, although published evidence is mixed. We conducted a meta-analysis to determine if any link between the use of pioglitazone and an increased risk of bladder cancer can be found. A comprehensive literature search was conducted through electronic databases as well as registries for data of clinical trials to identify studies that investigate the effect of pioglitazone on bladder cancer in diabetic patients. We used the risk ratio (RR) and the hazard ratio (HR) provided by the studies to illustrate the risk of occurrence of bladder cancer in the experimental group compared to that in the control group. Fourteen studies using RR and 12 studies using HR were included in the analysis. The overall RR was 1.13 with 95% CI (0.96-1.33) with low heterogeneity among the studies using RR, suggesting that no connection exists between use of pioglitazone and the risk of bladder malignancy. The summary HR was 1.07 (0.96-1.18) allowing us to affirm that there is no link between long-term use of pioglitazone and bladder cancer. Our results support the hypothesis of no difference in the incidence of bladder cancer among the pioglitazone group and the nonuser group. Our conclusion is that the explanation of hypothetically increased risk of bladder malignancy should be attributed to other factors.
Funding: Tchaikapharma High Quality Medicines Inc.
Keywords: Bladder cancer; Hazard ratio; Pioglitazone; Risk ratio; Type 2 diabetes.