Immune Biomarkers And Treatment (Tx) Outcome In Hormone Receptor-Positive (Hr Plus ) Breast Cancer (Bc) Patients (Pts) Treated With Preoperative Chemotherapy (Preop Chemo) Plus Bevacizumab (Bev).

e12134Background: Though preliminary study of the BC immune microenvironment suggests that HR+ tumors are less immune-active than other subtypes, immune biomarkers may have important clinical implications in HR+ BC pts. Methods: 78 HR+/HER2- BC pts were enrolled on a prospective trial of preop bev followed by bev with adriamycin/cyclophosphamide/paclitaxel dose-dense chemo. Tumor samples were collected at diagnosis and surgery (pre-tx and post-tx). PD-L1 expression (by immunohistochemistry) and tumor-infiltrating lymphocytes (TILs) were scored. Whole transcriptome sequencing and Nanostring PanCancer Immune Profiling Panel were performed. Pathologic response at surgery was assessed by Miller-Payne (MP) and residual cancer burden (RCB) scores. We calculated adjusted correlations by linear/logistic regression for RCB/dichotomized MP, respectively. Results: 55 pts who received trial tx and had u003e1 analyzable specimen are included. Pre-tx TILs and tumor PD-L1 (tPD-L1) scores (see table) were slightly positively...