Analysis of real-world PD-L1 testing in patients with urothelial carcinoma.

Abstract

447 Background: Programmed death-1/programmed death ligand 1 (PD-1/PD-L1) inhibitors are FDA-approved for urothelial carcinoma (UC) among other tumor types. PD-L1 immunohistochemistry (IHC) testing for UC has evolved with several diagnostic approvals. As of August 2018, the Dako PD-L1 IHC 22C3 pharmDx is a companion diagnostic, while the Dako PD-L1 IHC 28-8 pharmDx and the Ventana PD-L1 (SP263) assays are complementary diagnostics. The Ventana PD-L1 (SP142) assay has complementary status for platinum-treated patients with UC but gained companion status in July 2018 for cisplatin-ineligible patients with PD-L1-expressing UC. Here, we assess PD-L1 testing with the 22C3, 28-8, and SP142 assays on real-world UC samples. Methods: Analyses on 55,652 tumor samples from Symphony Health Solutions were performed between October 2015 and March 2018. PD-L1 results were linked to clinical characteristics using unique identifiers. PD-L1 testing on UC samples was performed at NeoGenomics Laboratories, Inc. based on the manufacturer’s protocols at the time. Results from the Dako assays were reported as % of tumor cells with PD-L1 expression. Test failure (TF) was defined as the absence of adequate sample with measurable PD-L1. Turnaround time (TAT) was defined as the time from sample receipt by the laboratory to test-report delivery. Paired 28-8 and 22C3 testing was performed on 13 samples. Results: 251 confirmed PD-L1 IHC tests (0.4% of tests conducted for the entire dataset) were performed on 223 UC samples, 98.2% of which had quantifiable PD-L1 expression. Mean TAT was 3.0 (1.0–4.2) days and the TF rate was 2.0% for all tests. The 22C3, 28-8, and SP142 assays were used in 52.2%, 9.6%, and 38.3% of tests, respectively. Paired testing with the 22C3 and 28-8 assays was highly correlated (Spearman’s r = 0.94; n = 13). Further analyses of UC PD-L1 prevalence will be presented. Conclusions: Based on the total tests conducted by this US national reference laboratory, PD-L1 testing was not commonly requested for UC during the analysis period. However, PD-L1 tests that were conducted displayed high success rates and reasonable TAT. This is the first comparison of the 22C3 and 28-8 assays on real-world UC samples, adding to the literature on PD-L1 testing concordance.