A study of immunohistochemical expression of PD-L1 in gastric carcinoma

Introduction and Aim: Aberrant over expression of PD L1 by tumours and tumour infiltrating lymphocytes provide an immune shield to the tumours. The present study aims to evaluate the effect of over expression of PD L1 in tumour cells and tumour infiltrating lymphocytes on various clinicopathological aspects of gastric carcinoma including the follow up and survival analysis.   Materials and Methods: Paraffin blocks were retrieved from 100 cases of primary gastric carcinoma who underwent curative resection. Immunostaining was done using a qualitative immunohistochemical assay from Ventana Roche with rabbit monoclonal anti PD-L1 clone SP142 intended for use in the assessment of the PD-L1 protein in formalin -fixed, paraffin -embedded (FFPE) tissue.   Results:    Out of 100 cases 65 were males and 35 were females. PD-L1 expression is observed in tumour cells in 17 cases and tumour infiltrating immune cells in 44 cases. Statistically significant correlation of expression of PD-L1 was observed with the clinicopathological characteristics like, larger tumour size (p value 0.03), lymphovascular invasion (p value 0.01), lymph node metastasis (p value 0.01) and higher tumour stage (p value 0.02). Two years follow up did not show any statistically significant correlation between PD-L1 expression in tumour cells and tumour infiltrating immune cells and survival (p value 0.27).   Conclusion:   Present study shows a substantial expression of PD-L1 in patients with gastric carcinoma. Hence PD-L1 immunohistochemistry can be potentially helpful in screening candidates for anti PD-L1 therapy.