Association between metformin use and risk of prostate cancer and its grade

David Margel*, David Urbach, Lorraine L. Lipscombe, Chaim M. Bell, Girish Kulkarni, Peter C. Austin, Neil Fleshner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


BackgroundMetformin is commonly prescribed to treat type 2 diabetes. Recent evidence suggests that it may possess antitumoral properties. The aim of this study was to test the association between metformin use and risk of prostate cancer and its grade among men with diabetes.MethodsData were obtained from population-based health-care administrative databases in Ontario, Canada. This retrospective cohort study used a nested case-control approach to examine the relationship between metformin exposure and the risk of prostate cancer within a cohort of incident diabetic men aged 66 years or older. We conducted four case-control analyses, defining case subjects as 1) any prostate cancer, 2) high-grade, 3) low-grade, and 4) biopsy-diagnosed. In each analysis, case subjects were matched to five control subjects on age and cohort entry date. Metformin exposure was determined based on prescriptions before cancer diagnosis, and adjusted odds ratios (aOR) were estimated using conditional logistic regression. All statistical tests were two-sided.ResultsWithin our cohort of 119 315 men with diabetes, there were 5306 case subjects with prostate cancer and 26 530 matched control subjects. Within the cancer case subjects, 1104 had high-grade cancer, 1719 had low-grade cancer, and 3524 had biopsy-diagnosed cancer. There was no association between metformin use and risk of any prostate cancer (aOR = 1.03, 95% confidence interval [CI] = 0.96 to 1.1), high-grade cancer (aOR = 1.13, 95% CI = 0.96 to 1.32), low-grade cancer (aOR = 0.94, 95% CI = 0.82 to 1.06), or biopsy-diagnosed cancer (aOR = 0.98, 95% CI = 0.84 to 1.02).ConclusionsThis large study did not find an association between metformin use and risk of prostate cancer among older men with diabetes, regardless of cancer grade or method of diagnosis.

Original languageEnglish
Pages (from-to)1123-1131
Number of pages9
JournalJournal of the National Cancer Institute
Issue number15
StatePublished - 7 Aug 2013
Externally publishedYes


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