Pioglitazone and bladder cancer: a propensity score matched cohort study

Aim: To examine whether exposure to pioglitazone use is associated with increased incidence of bladder cancer in patients with type 2 diabetes mellitus.

Method: A cohort study was done in the General Practice Research Database (GPRD) between 2001 and 2010. Two hundred and seven thousand seven hundred and fourteen patients aged ≥40 years with type 2 diabetes were studied (23,548 exposed to pioglitazone and 184,166 exposed to other antidiabetic medications but not pioglitazone). The association between pioglitazone and risk of bladder cancer was assessed by a Cox regression model. A propensity score matched analysis was done in a group of patients without missing baseline characteristics data.

Results: Sixty-six and 803 new cases of bladder cancer occurred in the pioglitazone and other group, respectively (rates of 80.2 (95% CI 60.8, 99.5) and 81.8 (95% CI 76.2, 87.5) per 100,000 person-years respectively). Pioglitazone did not increase the risk of bladder cancer significantly compared with the other antidiabetic drugs treatment group, (adjusted hazard ratio (HR), 1.16, 95% CI 0.83, 1.62). In a matched propensity score analysis in which both groups had similar baseline characteristics (17,249 patients in each group), the adjusted HR was 1.22 (95% CI 0.80, 1.84).

Conclusion: The results suggest that pioglitazone may not be significantly associated with an increased risk of bladder cancer in patients with type 2 diabetes.