The therapeutic candidate for immune checkpoint inhibitors elucidated by the status of tumor-infiltrating lymphocytes (TILs) and programmed death ligand 1 (PD-L1) expression in triple negative breast cancer (TNBC)

Background The status of tumor-infiltrating lymphocytes (TILs) is a prognostic factor for triple negative breast cancer (TNBC). Recent studies have shown that programmed cell death 1 (PD-1) or programmed death ligand 1 (PD-L1) is expressed on T lymphocytes or tumor cells modulating antitumor immunity. The regulation of immune checkpoints between tumor cells and T lymphocytes may serve as a target for improvement of TNBC prognosis. We investigated TILs and PD-L1 status in TNBCs before or after preoperative systemic therapy (PST) to elucidate the clinical significance of PD-L1 expression. Methods Ninety patients received PST, and materials of core needle biopsies (CNB) taken before PST were available for 32 patients. TILs were scored as “% stromal”, and tumors were defined as High-TILs (≥30%) or Low-TILs (