Immunohistochemical Expression of Programmed Death Ligand- 1 (PD-L1) in Colorectal Carcinoma; A Cross-sectional Study

Colorectal carcinoma (CRC) is one of the most common cancers worldwide. The interaction of programmed cell death receptor 1 (PD-1) and programmed death ligand 1 (PD-L1) plays an important role by inhibiting the immune mechanism by which cancer cells escape antitumor immunity. Immunotherapy using checkpoint inhibitors is a growing treatment modality in many cancers; one such is anti-PD1/PD-L1. The present study aimed to study the immunohistochemical (IHC) expression of PD-L1 in CRC and evaluate the association of PD-L1 expression in CRC with various known clinicopathological parameters.

It was a 2-year prospective study and included 34 colectomy specimens diagnosed as colorectal adenocarcinoma. The expression of PD-L1 was evaluated on tumor cells & tumor-infiltrating immune cells (TIICs) and correlated with various clinicopathological parameters.

Immunohistochemical expression of PD-L1 on tumor cells and tumor microenvironment in CRC revealed positivity in 17.65% of cases each. The PD-L1 expression on tumor cells was associated with lymphovascular invasion (LVI) and perineural invasion (PNI) with P- values of 0.012 and 0.005, respectively, while PD-L1 expression on TIICs was associated with tumor budding with P-value 0.022.

IHC expression of PD-L1 on tumor cells and immune cells was associated with some known poor prognostic factors. Since anti-PD1/PD-L1 is used for targeted therapy, it may be beneficial and economically feasible to evaluate PD-L1 in CRC and establish its role as a prognostic factor.