(HealthDay News) – For patients with type 2 diabetes, use of the oral hypoglycemic agent pioglitazone correlates with an increased risk of bladder cancer, with the risk increasing with duration of use.

To investigate the correlation between pioglitazone use and the risk of incident bladder cancer, Laurent Azoulay, PhD, from the Jewish General Hospital in Montreal, and colleagues conducted a retrospective cohort study involving 115,727 patients with type 2 diabetes, newly treated with oral hypoglycemic agents from January 1988–December 2009. Incident cases of bladder cancer were identified and matched with up to 20 controls.

During follow-up, the researchers identified 470 patients with bladder cancer. Of these, 376 cases that were diagnosed beyond one year of follow-up were matched with 6,699 controls. There was an increased risk of bladder cancer associated with ever use of pioglitazone (rate ratio, 1.83). Increasing duration of use correlated with an increase in the rate, with the highest rate seen for patients with more than 24 months of exposure (rate ratio, 1.99) and for those with a cumulative dosage >28,000mg (rate ratio, 2.54).

“The results of this study provide evidence that pioglitazone is associated with an increased risk of bladder cancer, whereas no increased risk was observed with the thiazolidinedione rosiglitazone,” the authors write. “The increased risk associated with pioglitazone became apparent after use for at least 24 months and receiving cumulative dosages >28,000mg.”

One author disclosed financial ties to the pharmaceutical industry.

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