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

Abstract

Background: 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). Aims: 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. Settings and Design: Tissue microarrays (TMA) were prepared from resection specimens of TNBC cases diagnosed from 2004 to 2008. Subjects and Methods: Immunohistochemical staining was performed on the TMA using the ventana PD-L1 antibody (Clone SP 263). Statistical Analysis: 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. Results: 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). Conclusion: 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.