Significance of PD-L1 expression in pulmonary metastases from head and neck squamous cell carcinoma

Abstract

BackgroundThe mechanism by which tumors escape the immune system has been actively investigated and is partly explained by the programmed death-1 (PD-1) and its ligand (PD-L1) pathway. This study is aimed at clarifying the prognostic significance of PD-L1 expression in patients with surgically resected pulmonary metastases of head and neck squamous cell carcinoma (HNSCC). Patients and methodsA retrospective review was conducted of 26 HNSCC patients who underwent complete resection of pulmonary metastases. PD-L1 expression in both the primary and metastatic tumors was evaluated using immunohistochemistry (anti-PD-L1 antibody, clone SP263). High PD-L1 expression was defined as ≥50% of tumor cells with positive staining. Survival and prognostic impacts following pulmonary metastasectomy were analyzed based on the PD-L1 expression level. ResultsThe patients included 23 men and 3 women, with a median age of 65 years. Six (23%) of the pulmonary metastatic cases showed high PD-L1 expression, while their corresponding primary lesions had low PD-L1 expression. The 5-year overall survival rate after pulmonary metastasectomy was 57.6% in all cases. The 5-year overall survival rates were 72.5% and 16.7% in the low and high PD-L1 groups, respectively (p < 0.001). Multivariate analysis demonstrated that high PD-L1 expression and older age (>65 years) correlated independently with a shorter overall survival (p < 0.001). ConclusionsHigh PD-L1 expression in pulmonary metastases could be an independent predictor of poor outcome in HNSCC patients undergoing pulmonary metastasectomy. This is the first report evaluating the prognostic implication of PD-L1 expression in metastatic HNSCC.