Background: Head and neck cancer has the third highest prevalence rate among tumors internationally, with significant rates of mortality and recurrence. The pathway of Programmed Cell Death Protein-1 (PD-1)/ Programmed Cell Death Ligand-1 (PD-L1) is essential in the mechanisms of tumor immune evasion. The expression of PD-L1 is linked to an immunosuppressive microenvironment and has a potential influence on immunotherapy.
Objectives: Evaluate the PD-L1 expression in tissue samples of nasopharyngeal and hypopharyngeal carcinomas.
Patients and methods: Sections of tissues sourced from 24 patients with hypopharyngeal carcinoma and 20 patients with nasopharyngeal carcinoma were tested for PD-L1 expression by immunohistochemistry. The level of expression was measured by a semi-quantitative scoring system and compared to adjacent normal mucosa. The relation of the PD-L1 expression with pathological and clinical parameters was examined.
Results: PD-L1 was found in all investigated tissue samples of both hypopharyngeal and nasopharyngeal carcinoma cases with absent expression in adjacent normal epithelium. PD-L1 histoscore varied from 50 to 280 with a mean (±SD) of 193 (±50) and median of 200. The correlation of PD-L1 expression had a higher grade (P = 0.002) with the advanced stage of hypopharyngeal carcinomas (P = 0.004).
Conclusion: Frequent PD-L1 expression in hypopharyngeal and nasopharyngeal carcinoma supports the claim that patients with these tumors could be potential candidates for immunotherapy.