Toronto | A drug used to treat diabetes may increase the risk of bladder cancer, according to a new study which suggests that the possibility increases with increasing duration of use and dose. Pioglitazone belongs to a class of drugs called thiazolidinediones that help to control blood sugar levels in patients with type 2 diabetes.
However, in 2005, a trial unexpectedly showed an imbalance in the number of bladder cancer cases with pioglitazone compared with placebo, researchers said. Since then, the association between the use of pioglitazone and bladder cancer has been controversial, with studies reporting contradictory findings, they said. Researchers from McGill University in Canada set out to determine whether the use of pioglitazone, when compared with other anti-diabetic drugs, was associated with an increased risk of bladder cancer in patients with type 2 diabetes.
They analysed data for 145,806 patients from the UK Clinical Practice Research Database (CPRD), who were newly treated with diabetes drugs between 2000 and 2013. Potential influential factors such as age, sex, duration of diabetes, smoking status and alcohol-related disorders, were taken into account.
Compared with no thiazolidinedione use, the use of pioglitazone was associated with an overall 63 per cent increased risk of bladder cancer (121 per 100,000 person years vs 89 per 100,000 person years), with the risk increasing with increasing duration of use and dose, researchers said.
In contrast, the use of a similar drug rosiglitazone was not associated with an increased risk of bladder cancer in any analysis, suggesting the risk is drug-specific and not a class effect, they said. Researchers suggest that doctors and patients should be aware of this association when assessing the overall risks and benefits of this therapy. The findings were published in the BMJ.