New Study Suggests Actos Bladder Cancer Link

Toronto, CanadaA new study published in the Canadian Medical Association Journal (CMAJ; 7/3/12) suggests a link between the use of Actos and bladder cancer. Previous studies also suggested Actos side effects could include an increased risk of bladder cancer, a finding that is apparently supported by this most recent study. Lawsuits have been filed against the maker of Actos, alleging patients were put at risk of Actos bladder cancer without being adequately warned.

The study involved conducting a systematic review and meta-analysis of biomedical databases and other literature for studies concerning the risk of patients with type 2 diabetes who take thiazolidinediones (a class of drug that includes Actos, known generically as pioglitazone) developing bladder cancer. Researchers noted that patients with type 2 diabetes already have a 40 percent increased risk of developing bladder cancer. "Thiazolidinediones, especially pioglitazone, may increase the risk," they wrote.

Among the studies that previously suggested an increased risk of bladder cancer in patients who used pioglitazone was the PROactive (PROspective pioglitAzone Clinical Trial in macroVascular Events), although that risk was not considered significant. Other studies, however, provided conflicting results as to whether or not Actos was associated with a higher incidence of bladder cancer. The CMAJ study's authors wrote that some studies have reported, "a significant increase, a nonsignificant increase and even a decreased risk of bladder cancer."

Researchers found that of 2,657,365 patients included in the study, 3643 had recently been diagnosed with bladder cancer. All five of the meta-analyses analyzed found either an elevated or significantly increased risk of bladder cancer in patients who used pioglitazone. Furthermore, some studies suggested that higher doses or increased treatment duration were associated with an increased risk of bladder cancer. As a comparison, researchers did not find an association between the use of rosiglitazone (a different thiazolidinedione) and bladder cancer.

"Our results suggest an association between pioglitazone use and bladder cancer in adults with type 2 diabetes," researchers concluded. They noted that although the absolute risk of bladder cancer is small, there are other treatments for type 2 diabetes that may be just as effective as pioglitazone but do not come with the same risk of bladder cancer.