Tumor-Infiltrating Lymphocytes and Programmed Cell Death - Ligand 1 in Breast Cancer

The morphological evaluation of Tumor-infiltrating Lymphocytes (TILs) in breast cancer is gaining momentum as evidence strengthens for the clinical relevance of this immunological biomarker. In breast cancer (BC) lesions, TILs are seen in intratumoral and stromal areas. TILs are predictive of response to treatment and this association appears to be strongest in Triple-negative (TNBC) and Her 2 (Human epidermal growth factor receptor) positive breast cancer subtypes. Contrastingly, the association in Estrogen Receptor (ER) positive, HER 2 negative tumors have not been established. Programmed cell death 1 (PD-1), are receptors expressed on the surface of T, B, and Natural killer cells and in some tumor cells. These attenuate the cellular immune response by inducing T-cell apoptosis. Programmed Cell Death Ligand 1 (PD-L1) overexpression is reported to be associated with large tumor size, lymph node metastasis, and ER-negativity. Importantly, PD-L1 is expressed more frequently in TNBC patients. High PD-L1 expression may be a prognostic indicator for reduced overall survival6. This information may be helpful to screen candidates for anti-PD-1/PD-L1 therapy, especially patients with TNBC The aim of this study is to characterize the cohort of patients with breast cancer based on a semiquantitative assessment of TILs and to correlate the concentration of TILs and PD-L1 in various intrinsic subtypes (based on Immunohistochemistry) with the overall outcome. Also to correlate the TILs and PD-L1 expression with tumor response to Neoadjuvant Chemotherapy (NACT) and to stratify the predictive value of this biomarker in TNBC.