More Studies Find Bladder Cancer Risk

Bladder cancer risks increased with pioglitazone use

(RxWiki News) People with type 2 diabetes have an elevated risk of several types of cancer, including liver and pancreatic cancer. The use of one diabetic medication increases the risk of another form of cancer.

The diabetes medication Actos (pioglitazone) increases an individual's risk of developing bladder cancer, according to two recently published studies.

It should be noted, though, that the absolute risks of developing bladder cancer are quite low.

"Learn about all your diabetes medication options."

Canadian researchers teased out specific data regarding diabetes meds and bladder cancer by conducting a systematic review and meta-analysis of randomized controlled trials and observational studies involving more than 2.6 million individuals.

"We observed an increased risk of bladder cancer associated with the use of thiazolidinediones [class of diabetes drugs]," writes one of the study's authors, Jeffrey Johnson, PhD with the School of Public Health at the University of Alberta.

"In particular, use of pioglitazone was associated with an increased risk of bladder cancer based on a pooled estimate from three cohort studies involving more than 1.7 million individuals," Dr. Johnson said.

Investigators also looked for a link between Avandia (rosiglitazone) and bladder cancer, but found none.

The other study, which was published in the May issue of the British Medical Journal.  Researchers found that of the 115,727 people who were taking oral diabetes agents, 470 of them were diagnosed with bladder cancer. 

Anyone who had ever used pioglitazone had greater risks of bladder cancer than the general public. These risks increased over time, with the highest rates being seen among those who took the drug for more than 24 months and those who took cumulative doses of more than 28,000 mg.  

Researchers found:

  • People who had ever taken Actos had an 83 percent increase in bladder cancer risks compared to those who had never taken the drug.
  • This equates to 74 cases of bladder cancer per 100,000 person-years compared to 73 cases per 100,000 in the general population.
  • For people who had taken Actos for two+ years, the rate was 88 cases per 100,000.
  • For those taking the drug at doses of 28,000+ mg, the rate grew to 137 cases per 100,000 person-years.

"Although the absolute risk of bladder cancer associated with pioglitazone was small, other evidence-based treatments for type 2 diabetes may be equally effective and do not carry a risk of cancer," the Canadian authors concluded.

Published July 3 in the Canadian Medical Association Journal, this research was supported by the Canadian Institutes of Health Research and the CIHR Institute of Nutrition, Metabolism and Diabetes. No financial conflicts of interest were reported. 

The British study was supported by grants from the Canadian Institutes of Health Research and the Canadian Foundation for Innovation. One author declared financial relationships with Novo Nordisk and Sanofi-Aventis.

Review Date: 
July 6, 2012