The tumor immune microenvironment differs between metastatic castrate resistant prostate cancer (CRPC) and hormone sensitive prostate cancer (HSPC).

Abstract

251 Background: Immune checkpoint inhibitors (CPIs) (anti-CTLA4, anti-PD-1/PD-L1 mAbs) have had limited monotherapy activity in prostate cancer (PC) compared to urothelial cancer (UC). Recent biomarker studies revealed molecular features associated w/ better efficacy/resistance to CPIs in UC.1 Here we examined the tumor immune microenvironment (iTME) of hormone naïve/sensitive (HSPC) & castrate resistant prostate (CRPC) specimens from primary & metastatic sites, to determine if parallels to UC molecular correlates exist that will allow us to predict subsets of PC pts who are more likely to benefit from rational combination therapies w/ CPIs. Methods: Tumor FFPE archival tissues (HSPC, n = 9..