Programmed Death Ligand-1 Combined Positive Score Concordance and Interrater Reliability in Primary Tumors and Synchronous Lymph Node Metastases in Resected Cases of [p16.sup.+] Oropharyngeal Squamous Cell Carcinoma

Context.--Pembrolizumab is used in patients with metastatic head and neck squamous cell carcinoma contingent upon the programmed death ligand-1 (PD-L1) combined positive score (CPS). Objective.--To compare PD-L1 CPS scores derived from paired resected primary tumors (PTs) and lymph node metastases (LMs) in patients with [p16.sup.+] oropharyngeal squamous cell carcinoma (OPSCC). Design.--We identified 38 resected [p16.sup.+] OPSCCs for which paired PTs and LMs were available. PD-L1 immunohistochemistry using the SP263 antibody clone was done on both the PT and the LM. CPS scoring was performed by 4 observers, and data were analyzed at the CPS cut points of greater than or equal to 1 and 20 in regard to interobserver and interspecimen agreement. Results.--Overall agreement between consensus CPS scoring of PT and LM was seen in 76% of paired specimens ([kappa] = 0.53). No specimen received a negative consensus score. Interobserver agreement for both PT and LM was fair to substantial ([kappa] = 0.54 and 0.51, respectively) and was inferior to that seen in a prospective series of unselected head and neck squamous carcinoma cases evaluated at our institution ([kappa] = 0.84). Conclusions.--Given the high rates of interobserver and interspecimen variability, evaluation of additional material or by additional observers may be of value in performing CPS scoring in cases of [p16.sup.+] OPSCC. This is particularly the case when a negative or low-positive result is being evaluated in a patient who is otherwise a good candidate for immunotherapy. doi: 10.5858/arpa.2021-0464-OA
Over the last several years, immune checkpoint inhibitors targeting the programmed death receptor-1 (PD-1)/programmed death ligand-1 (PD-L1) pathway have had a profound impact on the field of oncology. Immune checkpoint [...]