Analysis of real-world PD-L1 IHC testing for clinical use in patients across multiple tumor types.

Abstract

151 Background: A number of programmed death ligand 1 (PD-L1) IHC diagnostic tests have been approved by the FDA to guide treatment with programmed death-1/PD-L1 inhibitors. We evaluated PD-L1 assay utilization and concordance across all tumor types, including melanoma (MEL) and squamous cell carcinoma of the head and neck (SCCHN), using real-world cancer samples tested at a single reference laboratory in the United States. Methods: 55,652 samples with clinical characteristics were provided by Symphony Health Solutions. NeoGenomics Laboratories, Inc assessed PD-L1 expression using the Dako PD-L1 IHC 28-8 or 22C3 pharmDx, or Ventana PD-L1 SP142 assay tests between October 2015 and April 2018, according to the manufacturers’ protocols at the time of the study. Clinical characteristics were matched to PD-L1 test results using unique identifiers. Data were analyzed by BioStat Solutions, Inc. Results: 61,568 tests from 55,652 patients were included. Across all 61,568 tests, 88.8% were carried out with 22C3, 9.8% with 28-8, and 1.4% with SP142. The 28-8 and 22C3 pharmDx assays showed high analytical concordance in all 3113 matched samples with PD-L1 expression data for both assays (OPA = 96.2%, Spearman’s r = 0.96; Table). The failure rate across all tests was 3.5%, and 96.6% of patients had a quantifiable test result. Average test turnaround time was 3.1 days, with a 9.1-fold increase in total number of tests performed between Q4 2015 and Q1 2018 (from 1163 to 10,544). Subgroup analyses for 678 patients (1.2%) with MEL and 270 patients (0.5%) with SCCHN will be presented. Conclusions: Despite an increased demand for PD-L1 testing in the US, most patients received a result in 2–4 days. These real-world analytical data support the potential interchangeability of the Dako PD-L1 IHC 28-8 and 22C3 pharmDx assays in clinical practice for assessing tumor cell membrane PD-L1 expression across tumor types, and provide context on the evolution and adoption of PD-L1 testing for patients with cancer. [Table: see text]