Abstract
Background:
Men with diabetes may have a lower risk of prostate cancer than men without diabetes which may be altered by metformin use or race/ethnicity.
Methods:
Using administrative databases, from 1994 to 2012, adult (age⩾50 years) men with diabetes were identified. Metformin exposure was defined as a time-dependent variable, stratified first into any use, and into tertiles of cumulative dose. Surname algorithms identified individuals as Chinese or non-Chinese. Multivariable Cox regression estimated the risk of prostate cancer.
Results:
The cohort of 80 001 had a mean age of 64 years and median follow-up of 9 years. Chinese users of metformin aged 50–59, 60–69 and ⩾70 had similar risks of prostate cancer as non-users. Non-Chinese users aged 50–59 (adjusted hazards ratio (aHR): 0.86, 0.74 to 1.00) had a decreased risk whereas men aged 60–69 and ⩾70 did not. However, when metformin exposure was stratified into tertiles, there was no association in any strata except non-Chinese men aged 50–59 in the first (aHR: 0.68, 95% confidence interval (CI): 0.55, 0.84), second (aHR: 0.75, 95% CI: 0.61, 0.92) and third (aHR: 0.79, 95% CI: 0.64, 0.96) tertiles of metformin exposure and non-Chinese men aged 60–69 in the first (aHR: 0.81, 95% CI: 0.68, 0.95) tertiles of metformin exposure.
Conclusions:
There was no clear association between metformin and risk of prostate cancer in men with diabetes in either race/ethnicity. Our findings suggest a consistent relationship between metformin and prostate cancer across race/ethnicity.
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Acknowledgements
CBC was supported by a Canada Graduate Scholarships-Master’s Award from the Canadian Institute for Health Research. DTE Holds a Tier 2 Canada Research Chair in Chronic Disease Prevention and Management. SRM holds the Endowed Chair in Patient Health Management funded by the Faculties of Medicine and Dentistry and Pharmacy and Pharmaceutical Sciences of the University of Alberta. JAJ is a Senior Health Scholar with Alberta Innovates Health Solutions. JAJ will act as the guarantor.
Author contributions
CBC conducted the statistical analysis, wrote the manuscript and helped design the study. SRM, DTE and JAJ edited the manuscript and provided guidance throughout the study design and statistical analysis.
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Chen, C., Eurich, D., Majumdar, S. et al. Metformin and the risk of prostate cancer across racial/ethnic groups: a population-based cohort study. Prostate Cancer Prostatic Dis 20, 122–126 (2017). https://doi.org/10.1038/pcan.2016.65
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DOI: https://doi.org/10.1038/pcan.2016.65
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