Expression of PD-L1 (DAKO 28-8) in Urothelial Carcinoma of Urinary Bladder

Abstract

Introduction: Around 90% of bladder cancers are urothelial carcinoma. Recent advancements in treatment have shifted towards targeted therapies, particularly immunotherapies targeting PD-L1 (Programmed Cell Death Ligand 1). PD-L1, a ligand for PD-1 receptors, helps cancer cells evade the immune system. Various factors, including genetic alterations, lead to its upregulation in cancer cells. Immunotherapies aim to block this pathway, making cancer cells more susceptible to the immune response. Objective: The study was designed to assess the frequency of PD-L1 expression by immunohistochemistry in urothelial carcinoma of urinary bladder and its association with histological grades. Methodology: This study was conducted at Department of Pathology, Pakistan Institute of Medical Sciences Islamabad. Fifty-six cases of urothelial carcinoma were included. Immunohistochemistry using PD-L1 Dako 28-8 clone was applied to prepared tissue sections. PD-L1 positivity was determined by brown membrane staining in tumor cells, scored using the Tumor Proportion Score (TPS). Results: The median patient age was 63±7 years, with the highest frequency (58.9%) of PD-L1 expression occurring in the age range of 56 to 65 years. However, there was no significant association between PD-L1 expression and age groups. Out of 56 cases, 64.3% had a TPS (Tumor Proportion Score) of ≥5%. Among the 76.7% high-grade cases, 72% had a TPS ≥5%, whereas 28% had a TPS <5%. Among the 23.2% low-grade cases, 61.5% had a TPS <5%, and 38.5% had a TPS ≥5%. Conclusion: Sixty-four percent urothelial carcinoma cases showed PD-L1 expression. Significant association (p value = 0.02) between PD-L1 expression and high-grade urothelial carcinoma was found using Pearson’s Chi-square test.