Abstract B72: Metformin use and risk of biochemical recurrence following radical prostatectomy: Results from the SEARCH database
Authors: Allott Emma H. , Abern Michael R. , Gerber Leah , Keto Christopher J. , Aronson William J. , Terris Martha K. , Presti Joseph C. , Kane Christopher J. , Amling Christopher L. , Freedland Stephen J. 
Published: January 2014

Abstract
Introduction: Metformin is currently the drug of choice for management of type II diabetes mellitus. Recent epidemiological studies have reported that metformin use among diabetics decreases the risk of developing a variety of cancer types, including prostate cancer (PCa). However, the effect of metformin use on PCa outcome has yet to be clarified. The aim of this study was to investigate the association between pre-operative metformin use and biochemical recurrence (BCR) in a cohort of diabetic men who underwent radical prostatectomy (RP).
Methods: We performed a retrospective analysis of 337 men from the Shared Equal Access Regional Cancer Hospital (SEARCH) database treated for PCa with RP and with a diagnosis of diabetes prior to surgery. Cox proportional hazard models were used to assess time to BCR for diabetic men taking metformin in the year prior to RP compared to diabetic men not taking metformin. Models were adjusted for age, race, year of surgery, surgical center, pre-operative PSA and biopsy Gleason score.
Results: Of 337 diabetic men, 173 (51%) were taking metformin in the year before RP. The median follow-up among men who did not recur was 49 months, during which 112 men (33%) experienced BCR. Metformin use was associated with more recent year of surgery (median 2005 vs. 2001; p&lt;0.001) but not with age, race, BMI or biopsy Gleason score (all p&gt;0.1). Diabetics taking metformin had lower pre-operative PSA (p=0.12) yet higher prostate volume (p=0.17), relative to diabetics not on metformin, though these associations did not reach statistical significance. On unadjusted analyses, metformin use was not significantly associated with BCR (log-rank, p=0.29). After adjusting for multiple pre-operative features, metformin use in the year before surgery remained not related to BCR (HR 0.97, 95% CI 0.59 to 1.60, p=0.912).
Conclusion: In this cohort of diabetic men treated for PCa with RP, metformin use in the year prior to surgery was not significantly associated with time to BCR. Although this is the largest study to date to test the role of metformin among diabetics undergoing RP, larger studies with longer follow-up are needed to better assess whether metformin is associated with improved PCa outcomes, though the current study suggested no role for metformin for PCa control.
Citation Format: Emma H. Allott, Michael R. Abern, Leah Gerber, Christopher J. Keto, William J. Aronson, Martha K. Terris, Joseph C. Presti, Christopher J. Kane, Christopher L. Amling, Stephen J. Freedland. Metformin use and risk of biochemical recurrence following radical prostatectomy: Results from the SEARCH database. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr B72.