Programmed cell death ligand - 1 expression in triple negative breast carcinoma and its prognostic significance in Indian population.

Abstract

The programmed cell death protein - 1 (PD-1) - programmed cell death ligand - 1 (PD-L1) axis is emerging as a promising target for immunotherapy in triple-negative breast cancers (TNBC). We analyzed the expression of PD-L1 in TNBC cases, with special emphasis on lymphocyte-predominant tumors along with correlation of the same with clinicopathological features and outcome. Tissue microarrays (TMA) were prepared from resection specimens of TNBC cases diagnosed from 2004 to 2008. Immunohistochemical staining was performed on the TMA using the ventana PD-L1 antibody (Clone SP 263). Chi-square test was used for correlation of PD-L1 positivity in tumor and immune cells with clinicopathological features. Univariate and multivariate survival analyses were carried out using the Kaplan Meir and Cox Regression methods, respectively. Overall, PD-L1 staining was seen in 35.9% (66 out of 184) tumors. PD-L1 positivity of tumor cells was seen in 14.7% (27 out of 184 cases), whereas stromal immune cell expression was observed in 21.2% (39 out of 184) cases. Lymphocyte-predominant tumors showed statistically significant expression of PD-L1 in both tumor (P < 0.0001) and immune cells (P 0.036). On univariate analysis, PD-L1 in immune cells was associated with good overall survival (P 0.05) as well as disease-free survival (P 0.013). On multivariate analysis, the same was associated with a significantly decreased risk for recurrence (P 0.018). PD-L1 expression in stromal immune cells proved to be a significant prognostic factor for TNBC. This data can serve as a baseline to plan clinical trials with anti-PD-L1 drugs for TNBC in the Indian setting.