PURPOSE: Programmed cell death-1 ligand-1 (PD-L1) expression has been associated 
with prognostic implications in urologic malignancies. We aimed to investigate 
prognostic significance of pre- and post-treatment PD-L1 expression in patients 
treated with BCG for high-grade non-muscle-invasive bladder cancer (NMIBC).
METHODS: We reviewed a total of 141 high-grade NMIBC cases treated with 
transurethral resection +  ≥ 6 BCG instillations between 2004 and 2017. PD-L1 
immunohistochemistry (IHC) scoring was done on 0-3 scale, and cut-off for 
positive and high-level PD-L1 expression was set to ≥ 1% and ≥ 5% staining of 
tumor-infiltrating immune cells (IC), respectively. Clinicopathologic 
characteristics and oncologic outcomes [recurrence-free (RFS) and 
progression-free survival (PFS)] were compared, stratified by PD-L1 positivity. 
The prognostic role of PD-L1 was assessed using Kaplan-Meier, and univariate and 
multivariate Cox regression analyses.
RESULTS: Pre-treatment, 46.2% and 6.8% of high-grade NMIBC demonstrated positive 
and high-level PD-L1 expression, respectively. Positive PD-L1 expression was 
associated with submucosal invasion and refractory-tumor recurrence. PD-L1 
expression was not associated with RFS or PFS in regression analysis. 
Post-treatment, 55.1% and 11.6% of recurrent tumors demonstrated positive and 
high-level PD-L1 expression, respectively. Down-regulation of PD-L1 expression 
was noted in patients with refractory recurrence (p = 0.012).
CONCLUSION: Pre-treatment PD-L1 expression was associated with unfavorable 
pathological features in primary high-grade NMIBC and its expression level after 
BCG immunotherapy was significantly decreased in patients with refractory 
recurrence. PD-L1 expression did not have prognostic value for PFS or RFS; 
therefore, further research is necessary to identify novel biomarkers for 
prediction of disease outcomes in high-grade NMIBC.