Detecting PD-L1 protein expression by immunohistochemistry has shown to be effective in identifying patients who may benefit from treatment with PD-1 targeted immune checkpoint inhibitors. The PD-L1 IHC 28-8 pharmDx assay has been applied in formalin-fixed, paraffin-embedded (FFPE) squamous cell carcinoma of the head and neck (SCCHN) tissues for measuring PD-L1 expression and its associated treatment effect with nivolumab. Assay performance results of PD-L1 IHC 28-8 pharmDx in SCCHN, including validation in external reproducibility, are described.
Antigen retrieval was conducted on Dako PT Link and automated staining was performed with Autostainer Link 48 platform using the PD-L1 IHC 28-8 pharmDx protocol, per instructions for use. The PD-L1 staining was assessed by tumor proportion score to report the percentage of PD-L1 expression in invasive SCCHN. Assay performance was validated at the ≥ 1% expression level on commercially procured FFPE SCCHN specimens.
PD-L1 expression was measured on 236 unique specimens originating from squamous cell carcinoma of the tongue, tonsil, nasopharynx, oropharynx, hypopharynx, and larynx. The assay demonstrated acceptable sensitivity and reported a large range of PD-L1 expression from 0 to 95% positive tumor cells and 0 to 3+ staining intensity. Acceptable correlation was observed between primary and metastatic specimens and between “sister” blocks from the same patient. Validation of assay precision and robustness (to target retrieval solution pH, target retrieval solution temperature, target retrieval time, and cut section thickness) demonstrated agreement estimates above 97.5% with the lower bound of two-sided 95 percent confidence intervals at 95% or higher. When tested in external sites, intra- and inter-site reproducibility, and intra- and inter-observer agreements were estimated above 94% with the lower bound of two-sided 95 percent confidence intervals at 88% or higher. Stability of PD-L1 staining in aged cut sections demonstrated interim stability at 4 months with ongoing evaluation.
PD-L1 IHC 28-8 pharmDx has shown to be reproducible and robust in detecting PD-L1 expression in FFPE human SCCHN specimens using the Autostainer Link 48.
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Legal entity responsible for the study
Agilent Technologies, Inc.
Agilent Technologies, Inc. and Bristol Myers Squibb
S. Alvarez: Currently employed by a for-profit health care company, Agilent Technologies. Own stock in a for-profit health care company, Agilent Technologies. J. Chan, C. Felten: Employed, leader for, and has ownership in Gemini Diagnostics. Paid consultant for Agilent Technologies. J. William: Employed by a diagnostic laboratory, Neogenomics. Was in a paid consulting role for Agilent Technologies in the last 2 years. D.A. Hanks: Employed and holds leadership for Premier Pathology Laboratories, Inc. Employed by Agilent Technologies, Inc. Holds intellectual property relating to health and medicine in the last 2 years while working with Agilent Technologies. A. Northrup: Employed by Agilent Technologies and owns stock in Agilent technologies. Has been reimbursed for travel, accommodations, or other expenses by Agilent Technologies in the last 2 years. D. Jaiswal, M. Jansson, T. Phillips: Employed by Agilent technologies. And own stock in Agilent Technologies. A. Segal: Was employed by Agilent Technologies and owns stock in Agilent Technologies. I. Satnick, H. Little, B. Wynne, C. Pierce: Employed by Agilent Technologies. H. McDonald: Employed by Agilent Technologies. Was employed by Baster/Baxalta/Shire in the last two years. Owns stock in Shire, Inc. J. Carnahan: Employed by Agilent Technologies. Was employed by Agensys in the past 2 years and received research funding and paid travel expenses from Agensys. Owns stock in Amgen. S.Y. Reddy: Employed by Agilent and owns stock in Agilent Technologies. H.D. Inzunza: Was employed by Bristol-Myers Squibb and is employed by Halozyme. E. Oroudjev: Employed by Agilent Technologies. Is in leadership role for Agilent Technologies. Owns stock in Agilent Technologies.