Comparative analysis of PD-L1 expression and tumor-infiltrating lymphocytes between primary breast cancer and matched metastatic lesions: implications for immunotherapy

Our findings demonstrate systematic differences in immune parameters between primary and metastatic breast cancer sites, with reduced immune infiltration in metastatic lesions. The data suggest that targeting the PD-1/PD-L1 pathway may be particularly beneficial in patients with PD-L1+ TIL-high primary tumors, potentially by reinvigorating anti-tumor immune responses.