Immunohistochemical Expression of Programmed Death Ligand- ۱ (PD-L۱) in Colorectal Carcinoma; A Cross-sectional Study

Background & Objective: Colorectal carcinoma (CRC) is one of the most common cancers worldwide. The interaction of programmed cell death receptor ۱ (PD-۱) and programmed death ligand ۱ (PD-L۱) 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-PD۱/PD-L۱. The present study aimed to study the immunohistochemical (IHC) expression of PD-L۱ in CRC and evaluate the association of PD-L۱ expression in CRC with various known clinicopathological parameters.Methods: It was a ۲-year prospective study and included ۳۴ colectomy specimens diagnosed as colorectal adenocarcinoma. The expression of PD-L۱ was evaluated on tumor cells & tumor-infiltrating immune cells (TIICs) and correlated with various clinicopathological parameters.Results: Immunohistochemical expression of PD-L۱ on tumor cells and tumor microenvironment in CRC revealed positivity in ۱۷.۶۵% of cases each. The PD-L۱ expression on tumor cells was associated with lymphovascular invasion (LVI) and perineural invasion (PNI) with P- values of ۰.۰۱۲ and ۰.۰۰۵, respectively, while PD-L۱ expression on TIICs was associated with tumor budding with P-value ۰.۰۲۲.Conclusion: IHC expression of PD-L۱ on tumor cells and immune cells was associated with some known poor prognostic factors. Since anti-PD۱/PD-L۱ is used for targeted therapy, it may be beneficial and economically feasible to evaluate PD-L۱ in CRC and establish its role as a prognostic factor.