PD-L1 in oral squamous cell carcinoma: A key biomarker from the laboratory to the bedside

Objectives and background: Oral squamous cell carcinoma (OSCC) is a highly malignant disease with an increasing incidence. The need to improve therapeutic strategies for patients affected by OSCC is an urgent challenge. Currently, the advent of immunotherapy represents an important step toward this aim. Programmed cell death-ligand 1 (PD-L1), a membrane protein that can be expressed on tumor and inflammatory cells is a key biomarker whose expression is determined by means of immunohistochemistry and is necessary for selecting patients for immunotherapy. Methods: In this study, we review the methods of PD-L1 assessment and outcomes achieved with immunotherapy in the treatment of OSCC patients. Results: Based on a meta-analysis we demonstrate a lack of prognostic significance of PD-L1 in OSCC. Conclusions: We also highlight unresolved issues including difficulties in standardizing PD-L1 evaluation and discuss future opportunities such as leveraging digital pathology.