Letters Pioglitazone use and risk of bladder cancer

Don’t dismiss pioglitazone on basis of uncertain risk

BMJ 2016; 354 doi: https://doi.org/10.1136/bmj.i3667 (Published 06 July 2016) Cite this as: BMJ 2016;354:i3667
  1. Alison Gallagher, consultant physician and diabetologist1,
  2. Peter H Winocour, consultant physician and diabetologist1
  3. on behalf of the Association of British Clinical Diabetologists
  1. 1Association of British Clinical Diabetologists, ABCD Secretariat, PO Box 2927, Malmesbury SN16 0WZ, UK
  1. alison.gallagher{at}uhl-tr.nhs.uk

Tuccori and colleagues conclude that the use of pioglitazone is associated with increased risk of bladder cancer.1 However, in this study pioglitazone and non-pioglitazone users were not matched and, despite adjustment, pioglitazone users were older, had type 2 diabetes for longer, and had worse glycaemic control than non-pioglitazone users.2

It is worrying that, despite recent evidence to the contrary, the potential link between pioglitazone use and bladder cancer continues to be overstated.

The possible link between pioglitazone exposure and bladder cancer first came to light in the PROactive study.1 2 Yet, on exclusion of the five cases where bladder cancer developed within four months of starting pioglitazone, this suggestion was not upheld.2 A further study of over a million participants concluded that pioglitazone use was not associated with bladder cancer incidence.3

The prospective cohort KPNC study was established to tackle this issue: persuasively, a bladder cancer association was not seen over a 10 year period.4 NICE guidance, nonetheless, still states that the risk of bladder cancer with pioglitazone is 1-10/1000 cases.5 Reviewing this advice should be a priority for the NICE clinical guideline update committee.

The caveats of pioglitazone use should be balanced against its potential to improve glycaemic control and reduce cardiovascular and cerebrovascular risk in high risk patients.2 6 As new therapeutic possibilities emerge that reduce not only HbA1c but also cardiovascular outcomes and that perhaps work synergistically with pioglitazone,2 the role of pioglitazone should not be dismissed on the basis of a questionable risk of bladder cancer.

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References

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