Popular diabetes drugs may raise risk of bladder cancer

PHILADELPHIA, PA –  A popular class of diabetes drugs increases patients’ risk of bladder cancer, according to a new study.

The study, published online this month in the Journal of the National Cancer Institute, found that patients taking thiazolidinedione (TZDs) drugs are two to three times more likely to develop bladder cancer than those who took a sulfonylurea drug, another common class of medications for diabetes. TZDs account for 20 percent of the drugs prescribed to diabetics in the U.S.

Researchers from the Perelman School of Medicine at the University of Pennsylvania say the findings are especially important since diabetics are already at a slightly increased risk of this type of cancer.

A total of 60,000 Type 2 diabetes patients from the Health Improvement Network (THIN) database in the United Kingdom were analysed in the study. Patients treated with the TZD drugs pioglitazone (Actos) or rosiglitzaone (Avandia) for five or more years were found to have a two-to-three-fold increase in risk of developing bladder cancer compared to those who took sulfonylurea drugs. Among patients taking TZDs for that length of time, 170 patients per 100,000 would be expected to develop the disease, compared to about 60 in 100,000 of those who take sulfonylurea drugs.

Avandia was earlier linked to severe cardiovascular problems and most patients no longer use the drug. However, Actos is the ninth most commonly prescribed drug in the US, with 15 million prescriptions filed each year.

Previous data examining safety risks concerning Actos has already prompted the FDA to warn that it may be associated with a risk of bladder cancer, while France and Germany have removed the drug from their markets. The study add to mounting evidence against the entire class of TZDs, as one of the first studies examining this type of risk among people taking both types of TZDs and among those taking sulfonylurea drugs.