Clinical Performance And Utilization Of 3 Pd-L1 Immunohistochemical Assays

Three different PD-L1 immunohistochemical (IHC) assays have recently been approved to help guide treatment decisions regarding anti-PD-1 (Keytruda®, Opdivo®) and anti-PD-L1 (Tecentriq®) immuno-oncology based therapies. The three assays differ in the primary monoclonal antibodies used, the assay platform (Dako, Ventana), scoring and interpretation criteria, and intended use. Our clinical laboratories currently offer all 3 assays (pharmDx™ 22C3, pharmDx™ 28-8, and SP142) because they are associated with different intended uses, companion and complementary diagnostics for non-small-cell lung cancer (NSCLC), and complementary diagnostic for urothelial carcinomas (UC). In the NSCLC samples evaluated in the first year since the approval of the two pharmDx™ assays, we have noted a higher percentage of positive samples with the pharmDx™ 28-8 assay (50%) compared to the pharmDx™ 22C3 assay (30%). This difference is mainly due to the use of different assay cutoffs associated with the two assays, as there is good correlation between the overall staining patterns, including the distribution of the percentage of tumor cells exhibiting positive staining. For the SP142 assay tested on UC samples, 22% of the cases were considered positive. All 3 assays are robust, with a limited number of samples considered inconclusive ( Citation Format: Steven M. Anderson, Bruce Horten, Bryan McCune, Ronald Paler. Clinical performance and utilization of 3 PD-L1 immunohistochemical assays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 663. doi:10.1158/1538-7445.AM2017-663