Prognostic Significance of Programmed Cell Death-Ligand 1 Expression in Tobacco Associated Oral Squamous Cell Carcinoma: An Immunohistochemical Based Cross-Sectional Study.

Background: Advancements in immuno-oncology have dramatically transformed cancer treatment. Immunotherapy, targeting immune check point proteins, notably Programmed cell death ligand 1 (PD-L1) and its receptor Programmed Cell Death-1 (PD-1) which modulate the activity of immune response in Head and Neck squamous cell carcinomas (HNSCC), is an area of much research. The immunohistochemical expression of PD-L1 in cancer cells has been proposed as a predictive biomarker for selecting candidates for immunotherapy. Thus, the present study was undertaken to study the expression of PD-L1 in the primary tumour cells and evaluate its correlation with various clinicopathological parameters and prognosis in tobacco associated oral squamous cell carcinomas (OSCC).

Methods: Expression of PD-L1 was investigated in 75 surgically resected cases of OSCC by immunohistochemistry and its association with different clinicopathological features and prognosis was analysed.

Results: PD-L1 protein was detected in 68% (51 cases) of cases. Tumour stage (p = 0.04), lymph node (LN) metastasis (p < 0.01) and moderate to marked tumour infiltrating lymphocytes (TILs) (p < 0.05), significantly correlated with the PD-L1 expression in the primary tumour. PD-L1 expression did not show a significant association with overall survival (OS) rate, however, patients with positive PD-L1 expression showed a poorer survival rate. Patients exhibiting nodal positivity had the worst prognosis (p < 0.005).

Conclusion: These data demonstrated a significant association of ≥ 5% PD-L1 expression in the primary tumour and the presence of LN metastasis, moderate to marked TILs and advancing tumour stage, thus, making it a plausible immunotherapeutic target molecule in OSCC patients.