Do adults with DM II treated with pioglitazone have increased risk of bladder cancer?

Bottom line

This review of all available data found a much increased risk of bladder cancer among adults with type 2 diabetes treated with pioglitazone. Pioglitazone also significantly increases the risk of heart failure and there is minimal, if any, patient-oriented evidence of benefit from treatment (Richter B, et al. Cochrane Database Syst Rev. 2006 Oct 18;[4]:CD006060). Both the French and German governments have either suspended or strongly curtailed the use of pioglitazone. It lowers glycosylated hemoglobin levels, but I would not want my loved ones taking this stuff. (LOE = 2b)

Reference
Ferwana M, Firwana B, Hasan R, et al. Pioglitazone and risk of bladder cancer: A meta-analysis of controlled studies. Diabet Med 2013;30(9):1026-1032.

Study design: Systematic review

Funding source: Self-funded or unfunded

Setting: Various (meta-analysis)

Synopsis
Because of concern that pioglitazone is associated with an increased risk of bladder cancer, both the French and German medicine agencies have either suspended the use of pioglitazone or strongly advised physicians to stop prescribing it. These investigators thoroughly searched multiple databases (MEDLINE, EMBASE, the Cochrane Register, the FDA website, and Clinical-Trial.gov), reviewed bibliographic references of relevant articles, and contacted known researchers for longitudinal studies of patients with type 2 diabetes with or without exposure to pioglitazone. Two authors independently performed the search and evaluated both the methodologic rigor and the eligibility of individual trials. Disagreements were resolved by consensus discussion with a third reviewer. Both observational and experimental trials were included and sensitivity analyses were performed to assess the effect of study design and quality. Six articles (N = 215,142 pioglitazone users) met inclusion criteria, including one large randomized controlled trial, one prospective cohort study, and 4 retrospective studies. The retrospective studies included reports from large population-based databases, including the French health care system, Kaiser Permanente Northern California, the Taiwanese national health system, and the United Kingdom general practice research database. Follow-up occurred for a median of 44 months. Compared with the nonexposed group, bladder cancer occurred significantly more often among patients exposed to pioglitazone (hazard ratio = 1.23; 95% CI, 1.09-1.39; number needed to treat to harm = 20,903). The risk of bladder cancer was significantly increased with longer duration of pioglitazone use but not with increasing cumulative dosage.

David Slawson, MD
Vice Chair, Department of Family Medicine
University of Virginia
Charlottesville, VA

Copyright © 2013 John Wiley & Sons, Inc.

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