(UroToday.com) As the most common non-cutaneous cancer of men in the United States, prostate cancer affects the African-American population with higher incidence and higher prostate-cancer specific mortality than men, not of African ancestry. The reasons for the higher burden of disease and disparate outcomes have been attributed, in part, due to social, economic, environmental, and biological influences. The biological factors are still opaque, with retrospective data to suggest an improved response to certain therapies, including sipuleucel-T1, suggesting a possible difference in tumor-immune interaction. Rates of microsatellite instability (MSI)-high is low in prostate cancer overall, with a paucity of data in African-American prostate cancers specifically. The authors sought to indirectly evaluate potential response to immune checkpoint inhibition by measuring MSI using next-generation sequencing assays, Tempus xT (648-gene sequencing panel + whole-transcriptome RNAseq) and/or Tempus xF (105-gene targeted panel), on tissue or liquid compartment, respectively.