Abstract 1184: Association of immune microenvironment and race in the Carolina Breast Cancer Study

Background: High levels of tumor infiltrating lymphocytes have been associated with favorable prognosis in triple negative and HER2-positive breast cancer (BC), especially in tumors with high mutation burden. Recently, our group showed that TP53 functional defects are strongly associated with black race in the Carolina Breast Cancer Study (CBCS). However, the immune microenvironment has been inconsistently associated with racial disparities in BC. Methods: To characterize immune phenotypes in BC, we curated a 50-gene NanoString immune panel and validated the gene set using RNA sequencing data from The Cancer Genome Atlas (TCGA). We applied the NanoString panel in the CBCS and estimated associations with immune infiltrates, BC intrinsic subtype, proliferation scores, p53 mutation signature and race using relative frequency differences (RFDs) as the measure of association. Results: Our 50-gene immune panel produced sample groupings in TCGA similar to that observed with the deconvolution algorithm, CIBERSORT. In CBCS (n=1208), we identified three immune groups primarily defined by features related to either adaptive immunity, innate immunity, or a quiet immune environment. Confirming that our expression-based groups reflect the tumor immune microenvironment, these immune groups correlated with histological evidence of immune cells from H&E slides in both TCGA and CBCS. The adaptive-enriched group was strongly associated with young age (≤50 years), high tumor grade, higher proliferation scores and the basal-like intrinsic subtype. TP53 mutant-like status was strongly associated with the adaptive-enriched immune group (RFD: 25.3%, p