Study assuages pioglitazone bladder cancer fears
medwireNews: A study requested by the European Medicines Agency fails to find an association between pioglitazone treatment and bladder cancer risk in patients with Type 2 diabetes.
The study, undertaken by a consortium of European pharmacoepidemiologists, included data from Finland, the Netherlands, Sweden and the UK on 56,337 pioglitazone-treated patients and 317,109 patients never given the medication but matched for propensity to receive it.
In contrast to previous studies, “we used exact matching as well as propensity score matching to minimise treatment allocation bias”, write Pasi Korhonen (EPID Research, Espoo, Finland) and co-researchers in The BMJ.
“We included duration of treated diabetes, type and number of previous treatments, and history of diabetic complications as part of the matching algorithm with the aim of having a reference group that was as similar as possible.”
During an average follow-up of just under 3 years (maximum of around 11 years), the incidence of bladder cancer was 7.97 per 10,000 person–years among patients given pioglitazone, and 9.62 and 10.65 per 10,000 person–years in, respectively, 56,337 of the most closely matched nonusers and the 317,109 propensity-matched nonusers.
After adjustment for variables including use of other diabetes medications, there was no difference in bladder cancer risk between pioglitazone users and nonusers. There was also no association between duration of pioglitazone use and bladder cancer, with about 16% of cancers in users and nonusers occurring within the first 6 months of follow-up and 25% within 12 months.
Excluding these early, and presumably pre-existing, tumours had no effect on the findings, and there were no significant differences either across subgroups defined by age, gender and duration of diabetes, or when the team used different definitions of pioglitazone exposure.
The findings are in line with a number of other studies and are not subject to some of the limitations, such as short follow-up duration, of several of those that reported an increased risk, say Korhonen et al. However, they note that they lacked information on smoking status, body mass index and glycated haemoglobin levels for many of the study participants and that follow-up does not yet extend much beyond 10 years.
“These results provide additional important information on the safety of pioglitazone use in Europe”, the team concludes.
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