MP48-20: Protective Effects of Metformin against Biochemical Failure Following Radical Prostatectomy or Radiation Therapy in Localized Prostate Cancer

Linda My Huynh*, Orange, CA, Emily Keit, Omaha, NE, Erica Huang, Raymond Ceja Carrillo, Thomas Ahlering, Orange, CA, Shawna Boyle, Charles Enke, Michael J. Baine, Omaha, NE

Introduction: To assess the impact of metformin on biochemical failure (BF) in localized prostate cancers (PC) treated with radical prostatectomy (RP) or radiation therapy (RT).

Methods: 1,449 patients undergoing RP (n=1338, 92.3%) or RT (n=108, 7.5%) for localized PC at two institutions between July 2007 and January 2020 were evaluated for metformin use, demographic/oncologic characteristics, and biochemical outcomes. Androgen deprivation therapy was utilized per NCCN guidelines. BF rates were assessed overall and at 1, 3, and 5 years. Time to BF was estimated via Kaplan-Meier (KM); logistic regression and Cox proportionate hazards models were generated to adjust for significant differences.

Results: Of 1,449 patients, 148 (10.2%) utilized metformin at time of diagnosis. Patients on metformin were significantly older, had higher body mass indexes (BMI), and more aggressive disease (Gleason score (GS)>7). KM analysis at a mean ± SD follow-up of 3.6±2.6 years suggested that patients on metformin were less likely to experience BF at later timepoints (Tarone-Ware X2 =0.088); however, univariate analysis showed no differences in BF at 1, 3, and 5 years following treatment. 

After adjusting for age, BMI, preoperative PSA, and GS in multivariate analysis, patients on metformin were significantly less likely to experience BF at 5 years and overall. In Cox regression, metformin was independently associated with a 40% relative risk reduction in BF.

Conclusions: Metformin use was associated with increased age, higher BMI, and more aggressive PC. In multivariate analysis, metformin use was associated with a significant risk reduction in BF overall and at 5 years after treatment.

Source of Funding: NA