PD-L1 expression and FGFR-mutations among Danish patients diagnosed with metastatic urothelial carcinoma - a retrospective and descriptive study

Checkpoint inhibitors have changed the treatment landscape of advanced urothelial carcinoma (mUC), and recently a fibroblast-growth-factor-receptor (FGFR) inhibitor has been introduced. This study aimed at estimating programmed death-ligand 1 (PD-L1) expression in primary tumors (PTs) and the PD-L1 expression concordance between PTs and paired metastases in 100 patients with UC managed in the real-world setting. Further, the aim was to investigate FGFR1-3 aberrations and the correlation between FGFR1-3 aberrations and PD-L1 expression. PD-L1 immunohistochemistry was performed on 100 formalin-fixed paraffin-embedded archival primary UC samples and 55 matched metastases using the 22C3 PD-L1 assay. PD-L1 expression was determined by the combined positive score, considered positive at ≥10. Targeted next-generation sequencing on the S5+/Prime System with the Oncomine Comprehensive Assay version 3 was used to detect FGFR1-3 aberrations in PTs. We found that 29 of 100 PTs had positive PD-L1 expression. The PD-L1 concordance rate was 71%. FGFR1-3 aberrations were observed in 18% of PTs, most frequently FGFR3 amplifications or mutations. We found no association between FGFR1-3 aberrations and PT PD-L1 expression (p=0.379). Our data emphasize the need for further studies in predictive biomarkers.