To the Editor A prospective cohort study1 found no relationship between pioglitazone use and the development of bladder cancer, with a median follow-up of 6.1 years. The results are in contrast to the interim 5-year analysis of the study. The new result was not surprising given that the study design favored the null hypothesis.
First, the study excluded any person developing bladder cancer within 6 months of entry into the cohort. A meta-analysis of clinical trials performed by Takeda found that a significant number of patients get bladder cancer in less than 6 months’ duration of pioglitazone use.
Davies BJ. Pioglitazone Use and Risk of Bladder Cancer. JAMA. 2015;314(23):2568. doi:10.1001/jama.2015.13909