Immune Profiling Of Pre- And Post-Treatment Breast Cancer Tissues From The S0800 Randomized Neoadjuvant Trial Of Weekly Nab-Paclitaxel With Or Without Bevacizumab And Dose Dense Doxorubicin And Cyclophosphamide

578Background: We examined changes in the tumor immune microenvironment during neoadjuvant chemotherapy by comparing immune gene mRNA expression, tumor infiltrating lymphocyte (TIL) count and PD-L1 protein expression in pre- and post-treatment tissues. Methods: Paired pre- and post- treatment tumor samples from 60 patients were profiled using the Nanostring Immune Oncology 360 platform to measure the expression of 770 immune-related genes that also allowed us to test 14 immune cell type and 27 previously published prognostic and immuno therapy response predictive gene signatures. All samples were also assessed for TIL counts and PD-L1 protein expression by immunohistochemistry. Gene expression levels were compared by paired t-test with Bonferroni correction. TIL count, PD-L1 protein expression and immune gene signatures were compared using Wilcoxon signed-rank test. Baseline immune markers were correlated with pathologic complete response (pCR) using estrogen receptor (ER) and treatment adjusted logistic ...