(ChemotherapyAdvisor) – Long-term use of thiazolidinediones increases risk of bladder cancer in persons with type 2 diabetes, according to a team of researchers of the University of Pennsylvania, Philadelphia, PA. This conclusion is based on a study entitled “Association between Longer Therapy with Thiazolidinediones and Risk of Bladder Cancer: A Cohort Study,” which appeared online in The Journal of the National Cancer Institute on August 9. 

In this study, the investigators aimed to assess “the risk of bladder cancer associated with the use of thiazolidinediones (TZDs) and between pioglitazone and rosiglitazone, an alternative TZD.” The investigators met the aim by conducting a retrospective cohort study of patients with type 2 diabetes mellitus who initiated treatment with a TZD (n = 18,459 patients) or a sulfonylurea (SU) (n = 41,396 patients) over a 10 year period. Risk of bladder cancer in the TZD cohort was compared with the SU cohort.  

The study yielded no difference in bladder cancer risk between the 2 cohorts (TZD vs SU, HR = 0.93, 95% CI = 0.68–1.29). “However, the risk of bladder cancer was increased among patients with the longest duration of TZD vs SU therapy (≥5 years of use, HR = 3.25, 95% CI = 1.08–9.71) and among those with the longest time since initiation of therapy (≥5 years since first use, HR = 2.53, 95% CI = 1.12–5.77),” the investigators wrote. “Risk of bladder cancer also increased with increasing time since initiation of pioglitazone (P trend < .001) and rosiglitazone (P trend = .006).”

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The investigators concluded, long-term TZD therapy in patients with type 2 diabetes may be associated with an increased risk of bladder cancer.