Abstract PD6-06: Angiogenesis contributes to chemoimmunotherapy resistance in immune-high and immune-low triple-negative breast cancer (TNBC): Biomarker analysis of the NeoPACT trial

Abstract Background: Compared to immune-high TNBC, immune-low TNBC has lower pathologic complete response (pCR) rates and higher recurrence rates after neoadjuvant chemoimmunotherapy. Development of more effective therapies for immune-low early- stage TNBC is an area of unmet clinical need. Bispecific antibodies targeting PD-1/PD-L1 plus vascular endothelial growth factor (VEGF) are being evaluated in advanced TNBC. In this study we examined the prognostic role of an angiogenesis pathway expression signature in immune-high and immune-low early-stage TNBC treated with chemoimmunotherapy. Methods: 107 patients with TNBC treated with neoadjuvant chemoimmunotherapy (Carboplatin + Docetaxel + Pembrolizumab X 6 cycles) on the phase II NeoPACT trial (NCT03639948) with available pre-treatment +/- residual tumor whole exome RNA sequencing were included. Stromal tumor-infiltrating lymphocytes (sTILs) were scored by standard criteria, and tumors were defined as immune-high (Im-High; sTILs ≥30%) or immune-low (Im-Low; sTILs