Expression of PD-1/PD-L1 as predictive biomarker to immunotherapy response in patients with Head and Neck Squamous Cell Carcinoma (HNSCC): A systematic review

Introduction: The dismal survival rates seen in recurrent or metastatic HNSCC make it a significant worldwide health concern. Some individuals have had better results with newer treatments, including as immune checkpoint drugs that target the PD-1/PD-L1 pathway. The necessity for trustworthy prognostic biomarkers is underscored by the fact that responses are quite varied despite the therapy. Methods: In order to assess the predictive value of PD-1/PD-L1 expression in immunotherapy-treated HNSCC, this systematic review used the PRISMA standards. Important metrics such as objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) in connection to PD-L1 expression were evaluated in relevant clinical and translational trials that were located in extensive databases. Results: The reported ORRs were 17.2% to 40.9%. Improved response rates and survival outcomes were often linked to higher levels of PD-L1 expression, especially when measured using a combined positive score (CPS) of 20 or higher. Patient groups with low or negative PD-L1 expression did nevertheless show significant improvements. Conclusion: PD-L1 is a clinically useful but imperfect biomarker in HNSCC, supporting the need for standardized testing and integrated biomarker strategies to better guide immunotherapy selection.