Patient data is critical to establishing the risks and benefits of treatments. In this case, there is some evidence that a drug prescribed for diabetes, pioglitazone, leads to an increased risk of bladder cancer. At the moment, the nature of this link is unclear, so further research is critical for patients and clinicians alike.

Why was this work needed?

Pioglitazone is a drug commonly used by people with diabetes to lower their blood sugar. In 2011, an American study suggested that pioglitazone was linked with a significant increase in rates of bladder cancer. Subsequent research has tried to confirm whether or not pioglitazone really does raise the risk of bladder cancer but the situation is still unclear.

What happened?

Two recent studies have looked at the potential link between pioglitazone and bladder cancer.

In 2015, researchers used prescription data, cancer and mortality rates from people with Type 2 diabetes across six different regions from four different countries (three of the groups came from the UK) and did not find any evidence that pioglitazone increased the risk of bladder cancer.

In 2016, a different study looked at nearly 150,000 people who were treated with antidiabetic drugs between 2000 and 2013, and followed up until 2014. This work did identify an increased risk of bladder cancer with the use of pioglitazone.

What were the benefits?

Establishing the risks and benefits of treatments can take time – it is a challenging and complex process. More research is clearly needed to establish whether or not there really is a link between pioglitazone and bladder cancer, and the extent of this potential risk. High quality data will be fundamental to this ongoing research.

People with diabetes who may be suitable for pioglitazone should have conversations with their clinicians about weighing up the potential risks and benefits of this drug to them as individuals.

What type of data was involved?

Both pieces of research used the Clinical Practice Research Datalink (CPRD). In addition to using CPRD, the 2015 study also looked at data from two specific UK population groups, one from Scotland and one from Manchester, as well as data from Finland, British Columbia and Rotterdam. The Scottish dataset was drawn from a linkage between the data held in the Scottish Care Information-Diabetes Collaboration (a Scotland-wide Type 2 diabetes database) and cancer registry data which is held by the Information Services Division of NHS Scotland. The Manchester data was drawn from the Salford Integrated Record system.

CPRD is de-personalised before researchers are given access to it.

Who funded and collaborated on this work?

The 2015 study was funded by the European Foundation for the Study of Diabetes.

The 2016 study was funded by the Canadian Institutes of Health Research.

Where can I go for more information?

Pioglitazone and bladder cancer risk: a multipopulation pooled, cumulative exposure analysis

Pioglitazone use and risk of bladder cancer: population based cohort study