The Relationship Between Metformin and Serum Prostate‐Specific Antigen Levels |
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| Authors: | Viranda H Jayalath Christopher Ireland Neil E Fleshner Robert J Hamilton David JA Jenkins |
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| Institution: | 1. Clinical Nutrition and Risk Factor Modification Center, St. Michael's Hospital, Toronto, Ontario, Canada;2. Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;3. Department of Surgical Oncology‐Urology, Princess Margaret Cancer Center, Toronto, Ontario, Canada;4. Department of Surgery‐Urology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;5. Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada |
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| Abstract: | BACKGROUND Metformin is the first‐line oral antihyperglycemic of choice for individuals with type 2 diabetes. Recent evidence supports a role for metformin in prostate cancer chemoprotection. However, whether metformin indeed influences prostate biology is unknown. We aimed to study the association between metformin and serum prostate‐specific antigen (PSA) levels—the primary prostate cancer biomarker. METHODS We conducted a cross‐sectional study of 326 prostate cancer‐free men with type 2 diabetes were recruited between 2004 and 2013 at St. Michael's Hospital. Men were excluded if they had a PSA ≥10‐ng/ml, or used >2,550‐mg/d metformin or supplemental androgens. Multivariate linear regressions quantified the association between metformin dose and log‐PSA. Secondary analyses quantified the association between other antihyperglycemics (sulfonylureas, thiazolidinediones) and PSA; sensitivity analyses tested covariate interactions. RESULTS Median PSA was 0.9‐ng/ml (IQR: 0.5–1.6‐ng/ml). Metformin dose associated positively with BMI, HbA1c, diabetes duration, and number of statin, acetylsalicylic acid, diuretic users, and number of antihyperglycemics used, and negatively with LDL‐C. In multivariate models, PSA changed by ?8% (95%CI: ?13 to ?2%, P = 0.011) per 500‐mg/d increase in metformin. Men with diabetes for ≥6 years (n = 163) saw a greater difference in PSA per 500‐mg/d metformin (?12% 95% CI: ?19 to ?4%, P = 0.002], P‐interaction = 0.018). Serum PSA did not relate with sulfonylureas, thiazolidinediones, or total number of antihyperglycemic agents used. Our findings are limited by the cross‐sectional design of this study. CONCLUSIONS Metformin dose‐dependently inversely associated with serum PSA, independent of other antihyperglycemic medications. Whether metformin confers a dose‐dependent benefit on prostate tumorigenesis and progression warrants investigation. Prostate 76:1445–1453, 2016. © 2016 The Authors. The Prostate published by Wiley Periodicals, Inc. |
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| Keywords: | metformin prostate cancer PSA antihyperglycemic cross‐sectional dose‐response |
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