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Pioglitazone, rosiglitazone did not increase bladder cancer risk in patients with type 2 diabetes
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The cumulative use of pioglitazone or rosiglitazone to treat type 2 diabetes was not associated with bladder cancer in a pooled analysis of six populations, according to research published in Diabetologia.
“These data challenge the idea that pioglitazone causes bladder cancer,” Helen Colhoun, MD, of the University of Dundee, United Kingdom, told Endocrine Today. “We find no evidence of such an effect, at least in the time span of the study we have conducted, which was longer than many previously published.”
Helen Colhoun
Colhoun, with Daniel Levin, MD, also of the University of Dundee, and colleagues examined drug effects on bladder cancer risk using data from British Columbia, Finland, Manchester, Rotterdam, Scotland and UK Clinical Practice Research Datalink.
The investigators gathered prescription, cancer and mortality data from patients with type 2 diabetes. Data collected from six centers included 1.01 million patients during 5.9 million person-years; the mean age of the patients at entry into the centers was 60 to 64 years.
To model the effect of cumulative exposure on cancer incidence, a discrete time failure analysis was applied separately to data from each center with Poisson regression; time-dependent adjustments were made for ever use of pioglitazone; results were pooled using fixed and random effects meta-regression.
During a median follow-up of 4 to 7.4 years, there were 3,248 cases of incident bladder cancer, with 117 exposed cases.
No evidence was demonstrated for any association between cumulative exposure to pioglitazone and bladder cancer in men (RR per 100 days of cumulative exposure=1.01; 95% CI, 0.97-1.06) or women (RR=1.04; 95% CI, 0.97-1.11) with adjustments for age, calendar year, diabetes duration, smoking and any ever use of pioglitazone.
Further, no association seen between rosiglitazone and bladder cancer in men (RR=1.01; 95% CI, 0.98-1.03) or women (RR=1; 95% CI, 0.94-1.07).
“The decision to use any drug needs to weigh the risks and benefits associated with that drug,” Colhoun said. “We do not find evidence of bladder cancer being a concern with pioglitazone, but the decision to use the drug should be taken in the context of other known side effects, including fracture risk.”
Calhoun underscored that these data should provide reassurance for patients who have already used the drug and were worried by previous reports about bladder cancer.
The strengths of this particular research, according to investigators, were that “most observational pharmacoepidemiological studies are limited by allocation bias” and that they also “considered exposure to other glucose-lowering drugs in the models.”
Limitations to the study included short-term follow-up duration and absence of data on ethnicities other than white Europeans, BMI and smoking, the researchers conceded.
“Longer-term studies observational of real world exposure to diabetes drugs remain important, not just for this class of drugs, but other diabetes drugs too,” Colhoun said. “Such studies need to be careful to use methods that minimize biases.” – by Allegra Tiver
For more information:
Helen Colhoun, MD, MFPHM, FRCP, can be reached at Population Health Sciences, Medical Research Institute, The Mackenzie Building, Kirsty Semple Way, Dundee, DD2 4BF; email: H.Colhoun@dundee.ac.uk.
Disclosure: This study was funded by the European Foundation for the Study of Diabetes. Please see study for full list of researchers’ financial disclosures.
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Farhad Zangeneh, MD, FACP, FACE
Levin and colleagues, through pooled, aggregate-level analysis across multiple populations in several countries, found no significant association between cumulative exposure to pioglitazone and bladder cancer when using methods minimizing allocation bias.
No association with bladder cancer was seen in the 10-year data with higher cumulative doses of the drug or with longer time since initiation of therapy. This result was in contrast to an earlier 5-year interim analysis and a meta-analysis of four randomized trials that showed a significantly higher incidence of bladder cancer in long-term higher dose pioglitazone users.
Initially, when I heard about the association between bladder cancer and pioglitazone, I was doubtful. It didn’t make any sense to me, but you wait for additional data and science. Hearing this report makes better sense to me. There will be additional studies and debate on this subject. Truth in science and medicine is a constant variable.
The recent study and findings provide reassurance. I’m glad the cloud has been lifted. We are blessed to have numerous classes of agents, and thiazolidinediones have an integral, important role in the management of diabetes. They always have and likely will.
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