Abstract C009: Post-diagnostic statin and metformin use and risk of biochemical recurrence risk among Black and White men diagnosed with prostate cancer at the Veterans Health Administration
Authors: Khan Saira , Drake Bettina 
Published: September 2020

Abstract
BACKGROUND: Prostate cancer is the most common cancer among men in the United States. Black men represent a high-risk group that is more likely to be both diagnosed with and experience adverse prostate cancer outcomes. Both statins (to reduce cholesterol) and metformin (to treat diabetes) have been hypothesized to reduce the risk of biochemical recurrence (BCR), a clinically important outcome, among men with prostate cancer. However, few studies have examined this association specifically in Black men. Because Black men are at greater risk for adverse prostate cancer outcomes, the potential of commonly used medications, including metformin and statins, to reduce this increased risk needs to be investigated. Here, we have examined the potential of metformin and statins to reduce risk of prostate cancer recurrence in a racially-diverse cohort of men diagnosed with prostate cancer at the Veterans Health Administration (VHA). METHODS: Our cohort consisted of 20,359 Black and 52,004 White men that were diagnosed with prostate cancer between 1997-2009 at the VHA and received definitive treatment for prostate cancer (radical prostatectomy or radiation). Statin use and metformin use were defined as any statin or metformin prescription after prostate cancer diagnosis. BCR was defined using established definitions. (For men treated with radical prostatectomy, BCR was defined as a PSA of 0.2 ng/mL or higher for two consecutive assays without treatment. For men treated with radiation, BCR was defined as rise of 2 ng/ mL or more above the nadir achieved after radiation therapy.) Cox proportional hazard models adjusted for age at diagnosis, prostate cancer grade, prostate cancer stage, and locale (rural vs. urban) were used to assess the association between statin and metformin use. Statin and metformin use were analyzed in separate models, stratified by race. RESULTS: Statin use (69.9% of Black men; 75.4% of White men) and metformin use (29.4% of Black men; 24.3% of White men) were prevalent in our cohort. The mean BCR-free survival time was 5.7 years and 6.0 years in Black and White men, respectively, with 16.6% of Black men and 13.8% of White experiencing a BCR. Statin use was associated with a significantly reduced risk of BCR in the cohort as a whole (Hazard Ratio (HR): 0.87; 95% Confidence Interval (CI): 0.83, 0.91), Black men (HR: 0.84; 95% CI: 0.77, 0.90), and White men (HR:0.89; 95% CI: 0.84, 0.95). We observed no association between metformin use and risk of BCR [Overall (HR: 1.05; 95% CI: 1.00, 1.10), Black men (HR: 1.00; 95% CI: 0.93, 1.08), White men (HR: 1.05; 95% CI: 1.00. 1.11)]. CONCLUSION: Post-diagnostic statin use may reduce the risk of BCR in both Black and White men. This is one the few studies to examine statin use and metformin use specifically in Black men with prostate cancer. Importantly, because all patients treated at the VHA receive care regardless of insurance status, this study was able to control for socioeconomic status in ways other studies are unable.
Citation Format: Saira Khan, Bettina Drake. Post-diagnostic statin and metformin use and risk of biochemical recurrence risk among Black and White men diagnosed with prostate cancer at the Veterans Health Administration [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr C009.