When the Food and Drug Administration (FDA) last year issued a warning that the type 2 diabetes drug Actos (pioglitazone) was shown to increase users’ risk for bladder cancer, its warning was based on limited data from the Kaiser Permanente Northern California diabetes registry, the French national health information system, and the PROspective pioglitazone Clinical Trail In macroVascular Events study.
“None of the previous studies directly compared the TZDs (the class of drugs that includes Actos) with sulfonylureas (SUs), the common alternative therapy for type 2 diabetes not adequately controlled with metformin,” says Ronac Mamtani with the University of Pennsylvania.
The only other TZD currently on the market is Avandia (rosiglitazone), which was severely restricted by the FDA in 2010 because of heart attack risk.
To give a more accurate picture of the bladder cancer risk with Actos and other drugs in its class, Mamtani and colleagues conducted a study comparing TZDs with SUs. What they found gave more evidence of a link between Actos and bladder cancer.
Using The Health Improvement Network database, researchers conducted a retrospective study of nearly 60,000 patients with type 2 diabetes who received a prescription for either a TZD or SU between July 2000 and August 2010. Nearly 200 people were diagnosed with bladder cancer over 196,708 person-years of follow up with incident rates of 87.1 and 107.2 per 100,000 person-years with TZD and SU use, respectively. This led researchers to determine that there was no significant risk for bladder cancer between the two groups.
However, when researchers looked at long-term risk, those who had used TZDs for five years or more were more than three times more likely to develop bladder cancer than those who used the drug for less than one year. They also found that those who used TZDs long-term were at greater risk for developing bladder cancer than those on long-term SU therapy.
“The reproducibility of the findings from the U.S. and French studies, and now using UK data, provides support for the hypothesis that long-term treatment with the TZDs may be associated with an increased risk of bladder cancer relative to the common alternative therapy,” says Mamtani.
Researchers also noted that the risk of bladder cancer was similar in both Actos and the now-restricted Avandia.
Source: News Medical