Association between pioglitazone (PZD) therapy and bladder cancer (BC): A meta-analysis of epidemiologic evidence.

Abstract

4546 Background: There is evidence suggesting that PZD use may be a risk factor for BC, yet these reports are controversial. The aim of this meta-analysis is to review available data and evaluate the association between PZD and BC. Methods: Two independent reviewers conducted a systematic search of the Cochrane Library, OvidSP and PubMed for articles published January 1970 to April 2012. MeSH search terms included PZD, Actos, thiazolidinediones, diabetes mellitus (DM), and BC. Only studies reporting an effect measure for the association between PZD and BC were included. Subgroup analyses by study design and country were performed. Analysis was done using a random effect model after a preliminary review showed evidence of study heterogeneity. This was then assessed using the Cochrane’s Q and I2 statistics. Publication bias was evaluated using the Begg’s and Egger’s tests, and funnel plots. All analyses were performed using REVMAN 5.1. Results: A total of 6 studies (3 cohort and 3 case control) met the inclusion criteria. The overall pooled risk ratio (RR) for the association between PZD and BC was 1.12 (95% CI 1.09, 1.15; P <0.001). The summary RR for cohort and case control studies were 1.13(95% CI 1.07, 1.19; P <0.001) and 1.11(95% CI 1.07, 1.15; P <0.001), respectively. The subgroup analysis showed a significant association with BC in the USA and Europe, but not in Asia (RR 0.98, 95% CI 0.71, 1.34; P = 0.88). The association of PZD and BC was more sensitive for treatment duration (>12 month). Conclusions: Our study analyzed 1,214,071 patients, demonstrating a weak association between PZD and BC. The results were significant with increase in treatment duration, which corresponds to previous studies. This meta-analysis has limitations. Not all studies reported known variables associated with BC, such as smoking or occupational exposure. They did not address patient BMI, time from DM diagnosis or previous drug therapy. These parameters reflect severity of disease and level of insulin-resistance. Future studies should evaluate markers of insulin-resistance with PZD use and correlate with BC. Understanding the link between PZD and BC in the context of DM may allow physicians to determine a more accurate risk of PZD use.