Cytomembranic PD-L1 expression in locoregionally advanced nasopharyngeal carcinoma

Background and objective The aim of this study was to evaluate the expression of cytomembranic programmed death-ligand 1 (PD-L1) and its clinical significance in locoregionally advanced nasopharyngeal carcinoma (NPC). Patients and methods Formalin-fixed, paraffin-embedded tissue biopsies from 85 patients with histological diagnosis of locoregionally advanced NPC treated with radical intensity-modulated radiotherapy and concurrent cisplatin-based chemotherapy were studied. By using immunohistochemistry staining, expressions of cytomembranic PD-L1 on tumor cells were detected. Results After a median follow-up duration of 65.8 months, 7 (8.2%), 5 (5.9%), and 5 (5.9%) patients suffered from local failure, regional failure, and distant metastases, respectively. The 5-year local failure-free survival, regional failure-free survival, distant failure-free survival, and overall survival (OS) rates were 90.9%, 94.8%, 94.0%, and 92.2%, respectively. Our results revealed that a high expression of cytomembranic PD-L1 was correlated with shorter OS (5y-OS: 82.5% vs 97.6%, P=0.022). In the multivariate analysis, only the cytomembranic PD-L1 was an independent prognostic factor for OS (hazard ratio: 6.176, 95% confidence interval, 1.166-32.710, P=0.032). Conclusion Cytomembranic PD-L1 expression levels correlated with OS in locoregionally advanced NPC. Agreement between different methods is needed for further application of PD-L1 biomarker assays in NPC.