Pioglitazone treatment not linked to bladder cancer

by Bruce Sylvester: Treatment of diabetes with pioglitazone does not appear to be related to an increased risk of bladder cancer, researchers from an analysis including nearly 200,000 subjects reported in the July 21, 2015 issue of JAMA.

The investigators from Kaiser Permanente Northern California, Oakland, and colleagues evaluated retrospectively data from several studies of diabetes treatment, including  a bladder cancer study cohort of 193,099 persons

Among subjects in the bladder cancer study cohort, 34,181 (18 percent) received pioglitazone (median duration, 2.8 years) and 1,261 had incident bladder cancer.

The investigators found that “ever use” of pioglitazone was not associated with an increase in bladder cancer risk.

The authors concluded, “There was no statistically significant increased risk of bladder cancer associated with pioglitazone use. However, a small increased risk, as previously observed, could not be excluded.”

In an accompanying editorial, Phil B. Fontanarosa, M.D., M.B.A., Executive Deputy Editor of JAMA, and colleagues wrote, “The findings of the study by Lewis et al demonstrating no statistically significant association between the use of pioglitazone and the risk of bladder cancer are important because of the prevalence of type 2 diabetes, fairly widespread use of pioglitazone, and safety concerns about this drug.”

They continued, “Even though no observational study examining the relationship between an exposure and an outcome can definitively establish ‘positive’ cause-and-effect results, and no observational study can definitively prove ‘negative’ results, each study adds to the totality of evidence regarding the safety of drugs, devices, and vaccines. By publishing the results of these studies, JAMA will continue to provide information physicians can use in discussions with patients and regulatory bodies can use in policy decisions about the benefits and risks of various therapies.”