Determining PD-L1 expression in head and neck squamous cell carcinoma using immunohistochemistry

Area of Science:

• Oncology
• Immunology
• Pathology

Background:

• Advanced head and neck squamous cell carcinoma (HNSCC) presents limited therapeutic avenues.
• Tumor cell-expressed programmed death-ligand 1 (PD-L1) interacts with T-cell PD-1, promoting immune evasion and tumor survival.
• Immune checkpoint inhibitors targeting the PD-1/PD-L1 pathway offer a strategy for inducing tumor regression.

Purpose of the Study:

• To evaluate the utility of immunohistochemistry (IHC) for detecting PD-L1 expression in HNSCC.
• To assess PD-L1 expression as a potential biomarker for patient selection in immunotherapy.

Main Methods:

• Retrospective analysis of 93 HNSCC cases utilizing manual laboratory-developed technique (LDT) IHC for PD-L1 expression with the 22C3 antibody clone.
• Correlation of PD-L1 expression with clinicopathological parameters including age, gender, tumor site, grade, and stage.

Main Results:

• PD-L1 immunopositivity was observed in 59 (63.4%) of the 93 HNSCC cases.
• High PD-L1 expression (Combined Proportion Score [CPS] ≥50) was found in 15 (16.1%) cases, and low expression (CPS ≥1) in 44 (47.3%) cases.
• High interobserver agreement (Cohen's kappa = 0.910) was achieved for PD-L1 IHC scoring; no significant correlation was found between PD-L1 scores and patient/tumor characteristics.

Conclusions:

• Immunohistochemistry for PD-L1 detection is crucial for identifying HNSCC patients suitable for targeted immunotherapy.
• PD-L1 status assessment via IHC supports personalized treatment strategies in HNSCC management.