Evaluation of Programmed Death Ligand 1 Expression in Cytology to Determine Eligibility for Immune Checkpoint Inhibitor Therapy in Patients With Head and Neck Squamous Cell Carcinoma

摘要

BACKGROUND: Immune checkpoint inhibitors targeting the programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway have recently emerged as a frontline treatment for head and neck squamous cell carcinoma (HNSCC). The evaluation of PD-L1 expression by immunohistochemistry in histologic samples is used to determine the eligibility of patients with HNSCC for immunotherapy. Patients with newly diagnosed HNSCC are frequently diagnosed by fine-needle aspiration (FNA) of lymph nodes with metastatic disease. However, the evaluation of PD-L1 expression with the proposed combined positive score (CPS) has not been well established in cytology specimens. METHODS: This study retrospectively identified 21 HNSCC patients with a known PD-L1 status from histologic specimens and matched FNA specimens with tumor cells on cell blocks (CBs). The CB sections were stained with a PD-L1 antibody (22C3 clone). All cases were scored with CPS and the tumor proportion score (TPS). RESULTS: The data showed substantial concordance between cytologic and histologic specimens for CPS (agreement, 76.2; κ = 0.607) and TPS (agreement, 76.2; K = 0.607). With histology used as a reference standard, the positive predictive value was 100 for both CPS and TPS, whereas the negative predictive value was 57.1 for CPS assessments and 50 for TPS assessments. CONCLUSIONS: PD-L1 expression in HNSCC cytology samples has high concordance with paired histologic samples. PD-L1 CPS evaluation is feasible in HNSCC cytology CBs and can act as a surrogate for determining eligibility for immunotherapy in cases in which a histologic specimen is not readily available.