Reviews and reports

Pioglitazone raises risk of bladder cancer by 63%

A study published in the BMJ (31st March 2016) has found that a drug used to treat Type 2 diabetes, pioglitazone (Actos), may increase the risk of bladder cancer. The research found that the risk was higher for people taking larger doses and for those who take it for longer periods of time.

Pioglitazone and rosiglitazone (Avandia) belong to a class of drugs called thiazolidinediones. Avandia was suspended from the European market in 2010 after being linked to cardiovascular problems but this recent research did not show it had any increased risk of bladder cancer.

Actos, the history

  • The problems first surfaced in 2005 when a trial unexpected showed higher numbers of people with bladder cancer in those taking Actos compared to people taking a placebo.
  • These findings appeared in other but not all studies, so leaving some doubt about whether there actually was a link.
  • In 2011 the European Medicines Agency (EMA) carried out a safety review of Actos and concluded that it should continue to be prescribed for carefully selected patients and their response to the treatment should be monitored.

Uncertainty

The uncertainty led Canadian-led researchers to investigate whether Actos increases the risk of bladder cancer in people with Type 2 diabetes compared to other Type 2 medications. They analysed information from 145,806 people in the UK who started taking diabetes medication for the first time between 2000 and 2013 after removing other factors that could influence the results. They found:

  • The use of Actos (pioglitazone) was associated with a 63% higher risk of bladder cancer compared to people who did not take any thiazolidinediones class of medication.
  • This risk increased with higher doses and longer use.
  • Avandia (rosiglitazone) was not associated with an increased risk of bladder cancer suggesting that the risk is specific to Actos and not to the class of drugs.

Conclusions and recommendations

The researchers stress that in absolute terms the risk of bladder cancer with Actos remains low, in this case 622 people during the follow up period. They recommend that prescribing doctors should be aware of these risks and patients should be made aware so they can choose whether to remain on the drug. As ever, it is important patients are given all the information so that they can make an informed decision about their treatment options.