Discordance of high PD-L1 expression in primary and metastatic urothelial carcinoma lesions

Immune checkpoint inhibitors (ICI) targeting PD-(L)1 are effective in select patients with advanced urothelial carcinoma (UC). High PD-L1 expression enriches for response to ICIs; however, the predictive value of PD-L1 expression is limited, which may be due in part to dynamic expression of PD-L1 in the tumor environment. We sought to characterize PD-L1 expression in primary UC and paired metastatic lesions to gain insight into the potential discordance of tumor PD-L1 expression during the metastatic process. Materials and methods: Immunohistochemical staining for PD-L1 using the SP-142 antibody was performed on primary tumors and matched metastatic specimens in 77 evaluable subjects with advanced UC. Immunohistochemical staining was scored for the percentage of cells positive (