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Response: The Risk of Bladder Cancer in Korean Diabetic Subjects Treated with Pioglitazone (Diabetes Metab J 2012;36:371-8)
Sun Ok Song, Kwang Joon Kim, Byung-Wan Lee
Diabetes & Metabolism Journal 2012;36(6):462-463.
Published online: December 12, 2012
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Division of Endocrinology and Metabolism, Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.

Corresponding author: Byung-Wan Lee. Division of Endocrinology and Metabolism, Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Korea.

Copyright © 2012 Korean Diabetes Association

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

My colleagues and I thank the comments of Sang-Yong Kim and the emphasis on our study's limitations. We agree entirely with your opinions and also recognize the problems regarding the quality of the data.
Korea has one of the world's highest smoking rates (>40%) [1] and smoking is the greatest risk factor for bladder cancer [2]. Therefore, unlike other countries, the potency of pioglitazone on bladder cancer can be offset by smoking. Furthermore, the medical milieu in our country permits pioglitazone use only after or during concurrent treatment with metformin. Moreover, we are registered as a tertiary referral hospital of the National Insurance System in Korea, so we cannot analyze hazard ratios without checking precise doses. These confounding factors are potentially responsible for the inconsistency of our results with those of previous studies.
Previous large-scale clinical studies regarding pioglitazone use reported the possible increase of bladder cancer rates. However, this observation was meaningful only when pioglitazone dose was quantified, and not from solely its use [3-8]. Our study should be interpreted in the same context. In our study, we suggest that the risk of bladder cancer in Korean diabetics treated with pioglitazone might be different from that of other ethniticies. We could not have concluded that pioglitazone had no effect on bladder cancer risk because the odds of using pioglitazone were relatively high, although it was not significant. In addition, this study was a case-control designed study that reviewed electronic medical records in a hospital. We could not determine the dose-response relationship of pioglitazone on bladder cancer due to a lack of data and resources. The conclusion of risk stratification under pioglitazone use must be supported with data from National Health Insurance Corporation.
We were unsuccessful in obtaining insurance claims data from the National Health Insurance Corporation (or Health Insurance Review & Assessment Service) in order to analyze the effects of pioglitazone use on bladder cancer on a population-based level. Compared to other developed countries, there are many administrative obstacles for conducting population-based studies using insurance claims data in Korea. The awareness level of our government and/or public institutions, as well as that of the medical community, needs improvement. Without these improvements in awareness and changes in the social atmosphere, academic achievements will be limited.
These circumstances gave us no other choice but to pursue a large, multi-center study using our electronic medical records data. We are currently investigating additional data across the multi-institutional group, but for now, this is most optimal method of evaluating this relationship. We hope improvements in the governmental, medical, and social environments will help us overcome future problems in obtaining high quality data.

No potential conflict of interest relevant to this article was reported.

  • 1. World Health Organization. WHO report on the global tobacco epidemic, 2011 cited 2012 Nov 20. Available from:
  • 2. Dowdy D. Tobacco smoking and bladder cancer. JAMA 2011 306:2216-2217. author reply 2217. ArticlePubMed
  • 3. Zhu Z, Shen Z, Lu Y, Zhong S, Xu C. Increased risk of bladder cancer with pioglitazone therapy in patients with diabetes: a meta-analysis. Diabetes Res Clin Pract 2012;98:159-163. ArticlePubMed
  • 4. Kermode-Scott B. Meta-analysis confirms raised risk of bladder cancer from pioglitazone. BMJ 2012;345:e4541ArticlePubMed
  • 5. Tseng CH. Pioglitazone and bladder cancer: a population-based study of Taiwanese. Diabetes Care 2012;35:278-280. PubMedPMC
  • 6. Neumann A, Weill A, Ricordeau P, Fagot JP, Alla F, Allemand H. Pioglitazone and risk of bladder cancer among diabetic patients in France: a population-based cohort study. Diabetologia 2012;55:1953-1962. ArticlePubMedPMC
  • 7. Lewis JD, Ferrara A, Peng T, Hedderson M, Bilker WB, Quesenberry CP Jr, Vaughn DJ, Nessel L, Selby J, Strom BL. Risk of bladder cancer among diabetic patients treated with pioglitazone: interim report of a longitudinal cohort study. Diabetes Care 2011;34:916-922. PubMedPMC
  • 8. Azoulay L, Yin H, Filion KB, Assayag J, Majdan A, Pollak MN, Suissa S. The use of pioglitazone and the risk of bladder cancer in people with type 2 diabetes: nested case-control study. BMJ 2012;344:e3645ArticlePubMedPMC

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    • Comparison of the effect between pioglitazone and metformin in treating patients with PCOS:a meta-analysis
      Yifeng Xu, Yanxiang Wu, Qin Huang
      Archives of Gynecology and Obstetrics.2017; 296(4): 661.     CrossRef

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      Response: The Risk of Bladder Cancer in Korean Diabetic Subjects Treated with Pioglitazone (Diabetes Metab J 2012;36:371-8)
      Diabetes Metab J. 2012;36(6):462-463.   Published online December 12, 2012
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    Song SO, Kim KJ, Lee BW. Response: The Risk of Bladder Cancer in Korean Diabetic Subjects Treated with Pioglitazone (Diabetes Metab J 2012;36:371-8). Diabetes Metab J. 2012;36(6):462-463.

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