Study confirms increased risk of bladder cancer with diabetes drug

by Barbara Hewitt on April 19, 2016

Medical professionals should be aware that a common diabetes drug has been found to increase the risk of bladder cancer, scientists in Canada have warned.

The association between the drug pioglitazone and bladder cancer risk should be taken into account when assessing treatment so that all risks and benefits are discussed, said the team of researchers.

The study of British diabetics using the drug led by Dr. Laurent Azoulay, an epidemiologist at the Lady Davis Institute at the Jewish General Hospital and Associate Professor of Oncology at McGill University, suggests that the risk grows with increasing duration of use and dose.


The team also looked at a similar drug rosiglitazone but no increased risk of bladder cancer was found. However, this drug was withdrawn from use in 2010 due to an increased risk of cardiovascular disorders, including heart attack and heart failure.

Pioglitazone and rosiglitazone belong to a class of drugs called thiazolidinediones that help to control blood sugar levels in patients with type 2 diabetes.

In 2005, a trial unexpectedly showed an imbalance in the number of bladder cancer cases with pioglitazone compared with a placebo. Since then, the association between the use of pioglitazone and bladder cancer has been controversial, with studies reporting contradictory findings.

In an effort to clarify the discrepancies, Dr. Azoulay’s team 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 who were newly treated with diabetes drugs between 2000 and 2013 from the UK Clinical Practice Research Database (CPRD). 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% increased risk of bladder cancer. Overall 622 were diagnosed with bladder cancer during the follow up period with the risk rising with increasing duration of use and dose.

In contrast, the use of 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. These results remained largely unchanged after further sensitivity analyses.

“The results of this large population based study indicate that pioglitazone is associated with an increased risk of bladder cancer. But in absolute terms, the risk of bladder cancer remains low. But doctors and patients should be aware of this association when assessing the overall risks and benefits of this therapy,” said Dr. Azoulay.

The opinions expressed in this article do not necessarily reflect the views of the Community and should not be interpreted as medical advice. Please see your doctor before making any changes to your diabetes management plan.

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