Expression of Programmed Cell Death-1 (PD-1) and Its Ligand (PD-L1) in Breast Cancers and Its Association with Clinicopathological Parameters.

 Cancer immunotherapy targeting the programmed cell death ligand 1 (PD-L1) and programmed cell death-1 (PD-1) axis has revolutionized cancer therapy. PD-L1 also serves as a predictive marker for such therapy. To assess the potential of such therapy in any cancer, the positivity of PD-1 and PD-L1 in such cancers needs to be assessed. However, such studies for breast cancer are lacking in South Asia. We aimed to estimate the positivity of PD-L1 and PD-1 receptors in breast cancer and its various clinicopathological groups in our patient population.  We studied the immunoexpression of PD-1 and PD-L1 in 103 histologically proven invasive carcinoma breast cases from October 2018 to April 2019. The percent positivity of PD-1 and PD-L1 with 95% confidence intervals (CI) was estimated for all the cases as well as groups defined by stage, grade, molecular subtype, hormone receptor status, K -67, and age.  PD-1 positivity was seen in 72 (69.9%) cases (95% CI: 60.1-78.6). PD-L1 immunoexpression was seen in 61 (59.2%) cases (95% CI: 49.1-68.8) in immune cells and in 39 (37.9%) cases (95% CI: 28.5-50.0) in tumor cells. No significant association was found between PD-1, PD-L1 and age, overall clinical stage, grade, size, estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, and K -67. Moderate-to-high PD-1 and PD-L1 immunopositivity was seen in all subtypes of breast cancer.  PD-1 and PD-L1 is expressed in all subgroups of breast carcinoma. Patients in all such groups are amenable to immunotherapy, provided they are found suitable otherwise.