Abstract Introduction and study purpose: Prostate cancer (PCa) is the leading type of newly diagnosed cancer and second leading cause of cancer death in American men. Significant racial differences in PCa incidence and mortality have been long-reported in the U.S., with Black men demonstrating a disproportionately higher burden of disease compared to White men. Though some studies conducted in equal access health care settings have revealed equivalent PCa characteristics at diagnosis and comparable PCa outcomes for White and Black men. Identification of early predictors of prostate disease aggressiveness is essential to avoid over-treatment of clinically favorably disease that is unlikely to progress. This study examines the independent and joint roles of biological and social determinants of health (SDOHs) in predicting prostate disease aggressiveness in a racially diverse cohort of men undergoing biopsy for suspicion of PCa. Methodology: A retrospective cohort study was conducted at the University Hospitals Seidman Cancer Center in Cleveland, Ohio for the period January 1, 2005-May 2022. A retrospective chart review was conducted to identify eligible men, including White and Black men undergoing transrectal ultrasound-guided biopsy whose biopsy results included the following 3 groups: (i) negative biopsy with a history of 1+ negative biopsy (-ies) and no history of prostate cancer; (ii) biopsy-detected PCa of Gleason sum 6; and (iii) biopsy-detected PCa with metastases at initial cancer detection. Detailed clinical and biological specimen data were abstracted during retrospective chart review, and quantitative proteomics analysis of biopsy tissues is ongoing, using mass spectrometry, at the Pacific Northwest National Laboratory (PNNL). Multi-level modeling will be conducted to predict prostate disease aggressiveness as a function of protein biomarker candidates in combination with census block group-level SDOHs. Results: This study has achieved its initial goal of assembling a study cohort of 300 eligible men with available biopsy tissue, necessary clinical information, and full street address for assigning census regions. To date, proteomics data have been generated on the first 60 men (“Discovery cohort”) and SDOHs metrics have been linked to the first 180 men. Proteomic profiles and SDOH data will be examined jointly with SDOHs to predict patient clinical phenotype (i.e., metastatic, biopsy Gleason 6, biopsy negative). Conclusions: Identifying new markers of cancer aggressiveness within and across race has the potential to tailor disease management, and identify patients who are likely to benefit from earlier, timely treatment interventions, which will ultimately improve prostate cancer outcomes and quality of life. Predictive modeling that jointly considers biological determinants of cancer disparities in conjunction with neighborhood-level social factors have the potential to elucidate who can be safely spared repeat biopsies, as well as how to optimize cancer care. Citation Format: Jennifer Cullen, Tao Liu, Karin Rodland, Ranjini Ghosh, Anood Alfamy, Julia Payne, Kirsten Eom, Sweta Balaji, Nicole Diaz, Holly Hartman, Annie Liang Zhang, Daniel Spratt, Jonathan Shoag, Erika Trapl, Lee Ponsky, Gregory MacLennan. Biological and neighborhood-level social determinants of prostate disease aggressiveness among Black and White men undergoing prostate biopsy [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr C088.