Prognostic Role of PD-L1 Expression in Oral Squamous Cell Carcinoma Varies by Oral Compartments and Immunostaining Patterns: A Meta-analysis

Abstract

Blocking the PD-L1/PD-1 pathway efficiently enhanced antitumor immunity that reduced tumour growth and improved survival, whereas the prognostic roles of PD-L1 positivity in oral squamous cell carcinoma (OSCC) were controversial. This study aimed to determine the clinicopathological and prognostic significance of PD-L1 expression in tumor cells (TCs) or tumor-infiltrating lymphocytes (TILs) of OSCC. The systematic retrieve was performed for seeking suitable studies through PubMed, Web of Science, the Cochrane Library and Scopus. 46 studies were ultimately included in the meta-analysis. This study showed that the levels of PD-L1 expression in TCs were relatively high in femal patients (P <0.001), non-smoker (P <0.001), non-drinkers (P =0.037), advanced stage (P =0.028), N+ status (P =0.027), and tumours with high levels of PD-1 (P =0.024), and CD8+ (P =0.022). High PD-L1 expression in TCs had significant effect on worse LRFS (P=0.004), and also was more likely to have worse OS in Asia (P =0.018). Both DSS (P =0.035) and DFS (P =0.003), at a 5% cut-off of PPC, had positive association with high PD-L1 expression. The results of OS showed that a worse prognosis for 5H1 (P =0.032), and a favourable prognosis for 22C3(P =0.001). E1L3N was shown to be associated with an worse DSS (P =0.014). High expressions of PD-L1 in TCs had a worse OS (P =0.023) and DFS (P =0.003) in OSCC of the tongue. Consequently, future study should especially consider oral compartments and methods for PD-L1 immunostaining as confounding factors when observing PD-L1 of response to anti-PD1 therapy.