The US Food and Drug Administration (FDA) said today that it still believes the type 2 diabetes drug pioglitazone (Actos, Takeda Pharmaceuticals) may pose an increased risk for bladder cancer after updating its review of published research, which has gone back and forth on the issue.
The agency added a warning about the increased risk for bladder cancer to the drug's label in 2011 based on interim results of a 10-year epidemiological study of patients with diabetes in the database of Kaiser Permanente (KP) of Northern California. The data suggested that this cancer risk rose as the dose and treatment duration increased. The revised label advises clinicians not to prescribe pioglitazone for patients with active bladder cancer and to exercise caution when using it in patients with a history of the cancer.
Several subsequent studies rebutted the causal link between pioglitazone and bladder cancer, one in 2014, and another in 2015. The latter study, published in the Journal of the American Medical Association, looked at the full 10 years of data drawn from the KP database but could no longer find the cancer signal detected in the interim results.
However, the pendulum swung in the warning direction again when a retrospective cohort study published in the BMJ earlier this year reported a 63% higher risk for bladder cancer for pioglitazone, with longer duration and larger doses increasing the risk.
The FDA said in a news release that after analyzing the new data since 2011, it has concluded — again — that pioglitazone may be linked to an increased risk for bladder cancer. The agency will update the drug's label to describe the additional studies it reviewed.
The risk-benefit calculation for pioglitazone has gotten more complicated in 2016, and not just in terms of risk. A study published in February in The New England Journal of Medicine reported that the drug lowers the risk for recurrent stroke or myocardial infarction in patients with insulin resistance, no frank diabetes, and a history of stroke or transient ischemic attack. At the same time, patients receiving pioglitazone also had higher rates of weight gain, edema, and bone fractures requiring surgery or hospitalization.
More information on today's FDA announcement is available on the agency website.