Pioglitazone use and the risk of bladder cancer

This study aimed to identify the risk association between pioglitazone exposure and bladder cancer. A nested case–control study was performed using a representative database randomly sampled from National Health Insurance enrollees. The source cohort consisted of newly diagnosed diabetic patients from 1997 to 2009. Cases were identified as those with a diagnosis of bladder cancer from 2002 to 2009. For each case, four matched control individuals were randomly selected. A multiple logistic regression model was used to estimate the relative magnitude of risk in relation to the use of pioglitazone. In total, 259 cases and 1036 controls were identified. The prevalent use of pioglitazone is similar in cases and controls (adjusted odds ratio, 1.20; 95% confidence interval, 0.58–2.49). Compared to nonusers, these values were 1.08 (0.41–2.88) for those with cumulative pioglitazone use ≤ 8268 mg and 1.35 (0.48–3.79) for those with cumulative pioglitazone use > 8268 mg. This study does not provide support for the risk association between pioglitazone exposure and bladder cancer. Further confirmation is needed due to the limitation of small case number with relatively shorter exposure duration and lower cumulative dose.