Programmed death ligand-1 expression is associated with stage and histological grade of parotid carcinoma

Background: The immune checkpoint ligand programmed death ligand-1 (PD-L1) is expressed by various cancers, including those of the head and neck. However, the role of PD-L1 is still unknown. Objectives: To investigate the relationship between PD-L1 expression and survival rate in parotid carcinoma. Methods: PD-L1 expression was investigated by immunohistochemical analysis in 127 patients with parotid carcinoma. The relationship between PD-L1 expression and stage, histological grade, and survival was assessed. Results: PD-L1 expression was found in 28.3% of parotid carcinomas, with the expression being higher in tumors with a higher stage, a higher-grade, and node positive cases. However, the 5-year disease-specific survival rate was 82.2% for the patients with PD-L1 positive and 86.9% for those with PD-L1 negative tumors, showing no significant difference. Conclusions: PD-L1 expression was positive in approximately 50% of high- grade carcinomas, which was similar to the level in head and neck squamous cell carcinoma. In patients with other cancers, it has been reported that an anti-PD-1 monoclonal antibody was more effective against tumors with higher PD-L1 expression. Therefore, it could be a possible new therapeutic option for patients with highly malignant parotid tumors that have a poor prognosis.