A single-arm, single-institution study to induce phenotypic changes in the tumor microenvironment by delivering 8Gy partial breast irradiation in immune-cold triple-negative breast cancer confirmed by PD-L1 and TILs. Additional tissue biopsy will be performed following radiation therapy. Subsequently, neoadjuvant chemotherapy including Pembrolizumab will be administered to evaluate whether pathological complete response rates are improved.
Breast cancer patients aged 20 years or older with clinical stage IIA or higher on imaging studies
Patients with triple-negative breast cancer confirmed on tissue biopsy
Cold immune tumor environment with tumor-infiltrating lymphocytes (TILs) <30% and PD-L1 Combined Positive Score (CPS) <10 on immunohistochemical staining of biopsy specimens
Patients with no prior history of breast cancer
Patients with non-triple-negative breast cancer on tissue biopsy
Patients scheduled for surgery without neoadjuvant chemotherapy
Patients with TILs ≥30% or PD-L1 CPS ≥10 on immunohistochemical staining of biopsy specimens (immune-hot tumor)
Patients with recurrent breast cancer or de novo stage IV disease