Predictive value of tumor-infiltrating lymphocytes (TILs) and programmed cell death-ligand 1 (PD-L1) expression in breast cancer patients treated with neoadjuvant chemotherapy

Abstract Introduction Immune system plays an important role in behavior of cancer. Breast cancer and its stroma display high levels of immune-cell infiltrates (tumor-infiltrating lymphocytes TILs). Programmed cell death-ligand 1 (PD-L1) is one key inhibitor mechanism for TILs. Potential of TILs and PD-L1 as predictive factors for chemotherapy response in breast cancer is a promising field of study. The aim of this work is to investigate the correlation of PD-L1, TILs and pathologic response following neoadjuvant chemotherapy (NAC) in breast cancer patients and effect of NAC on PD-L1 expression and TILs in residual tumor mass. Methods Thirty patients with invasive duct carcinoma diagnosed by core biopsy and received NAC were enrolled in this prospective study from November 2018 to October 2020. PD-L1 expression was evaluated by immunohistochemistry and relates this to TILs, clinical characteristics, and response to neoadjuvant chemotherapy and then re-evaluated in residual masses after surgery. Results PD-L1 expression was observed in 40% of cases in the tumor cells. High stromal TILs were detected in 46.7%. Also, 64.3% and 58.3% of patients expressed TILs and PD-L1 (respectively) in their core biopsies gained complete clinical and pathologic responses with significant difference (p value  Conclusion High TILs and PD-L1 are associated with complete clinical and pathologic responses in breast cancer patients who receiving NAC.