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Diabetes Drugs Increase Risk of Bladder Cancer

Evidence mounts against thiazolidinedione class

A popular class of diabetes drugs increases patients’ risk of bladder cancer, according to a new study announced on August 13 and published online in the Journal of the National Cancer Institute.

Researchers at the University of Pennsylvania’s Perelman School of Medicine found that patients taking thiazolidinedione (TZD) drugs are two to three times more likely to develop bladder cancer than those taking a sulfonylurea drug, another common class of diabetes medication. TZDs account for up to 20% of the drugs prescribed to diabetics in the U.S.

The authors say the findings are especially important since diabetic patients are already known to be at a slightly increased risk of bladder cancer compared with the general population.

A total of 60,000 patients with type 2 diabetes were evaluated from The Health Improvement Network (THIN) database in the U.K. The researchers found that patients treated with the TZD drug pioglitazone (Actos) or rosiglitazone (Avandia) for 5 or more years had a twofold to threefold increase in the risk of developing bladder cancer compared with those who used sulfonylurea drugs. Among patients taking TZDs for that length of time, the researchers’ analysis indicates that 170 patients per 100,000 would be expected to develop bladder cancer, compared with about 60 per 100,000 of those taking sulfonylurea drugs, such as glipizide (Glucotrol).

Pioglitazone is the ninth most commonly prescribed drug in the U.S., accounting for about 15 million prescriptions each year. The medication is a common choice when type 2 diabetes can no longer be controlled with the first-line diabetes drug metformin. The FDA has already warned that pioglitazone may be associated with a risk of bladder cancer, and France and Germany have removed the drug from their markets.

The new findings add to mounting evidence against the entire class of TZDs.

For more information, visit the Perelman School of Medicine Web site.

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