Background: Pre-existing DM is associated with increased PCa specific and all-cause mortality in men with prostate cancer (PMID: 27652121). However, the underlying reasons are unclear. We hypothesized that transcriptomic profile of metastatic PCa pts with diagnosis of DM prior to the diagnosis of metastatic disease and start of systemic therapy will be different from those without DM. Methods: In this IRB-approved retrospective study, advanced PCa pts with available RNA profiling of treatment naïve tumor tissue through a CLIA-certified laboratory were included. Based on pre-existing DM prior to onset of metastatic disease, pts was grouped into DM and non-DM. Differential gene expression analysis between the two groups was performed using DeSeq2. These results were subjected to Gene Set Enrichment software analysis (GSEA) to identify pathways enriched in each cohort. Gene ontology analysis using TopGO software was done to identify the biological process occurring at the molecular level of these differentially expressed genes. All bioinformatic analysis was conducted in R studio, version 4.1.1. Results: 75 pts were eligible and included: 20 DM vs 55 non-DM. Baseline characteristics (DM vs non-DM): median age 63.5 vs 64 years; median PSA at diagnosis 20 vs 18.85ng/mL; de novo disease: 55% vs 43.6%; Gleason score ≥8: 60% vs 74.5%. DM pts had upregulation of the following pathways: TNF alpha signaling, inflammatory response, IL-6 JAK STAT3 signaling, heme metabolism, and the p53 pathway vs non-DM pts. Gene ontology analysis and individual differential gene expression profiles will be reported at the meeting. Conclusions: Our study found that pre-existing DM is associated with upregulation of inflammatory pathways in pts with PCa These hypothesis-generating results need external validation. Identification of transcriptomic biomarkers in these subsets of pts may help with further drug development.