Despite smaller, prior studies suggesting that pioglitazone might raise users’ risk of bladder cancer, a large new study finds no statistically significant association. The research was published in the Journal of the American Medical Association.

Certain prior studies had suggested an increased risk of bladder cancer with the use of pioglitazone. A team led by Assiamira Ferrara, M.D., Ph.D., of Kaiser Permanente Northern California in Oakland, examined long-term data from 193,099 diabetes patients.

The researchers found no statistically significant association between taking the medication and increased risk of bladder cancer.

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However, a small increased risk could not be ruled out, the investigators said. The also analyzed long-term data from another group of 236,507 diabetes patients and found that taking pioglitazone was associated with a 41 percent increased risk of pancreatic cancer and a 13 percent increased risk of prostate cancer.

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“Pioglitazone use was not associated with a statistically significant increased risk of bladder cancer, although an increased risk, as previously observed, could not be excluded,” the authors write.

“The increased prostate and pancreatic cancer risks associated with ever use of pioglitazone merit further investigation to assess whether they are causal or are due to chance, residual confounding, or reverse causality.”

The study was funded by Takeda, which manufactures pioglitazone.


  1. Lewis JD, Habel LA, Quesenberry, CP, et al. Pioglitazone Use and Risk of Bladder Cancer and Other Common Cancers in Persons With Diabetes. JAMA. doi:10.1001/jama.2015.7996. July 21, 2015.