PD-L1 Dako 28-8 and 22C3 assays and Ventana SP263 assay gave comparable results across dedicated platforms for PD-L1 presence in tumor and immune cells, according to results presented at the International Association for the Study of Lung Cancer (IASLC) 17th Annual World Conference on Lung Cancer in Austria.1
Julien Adam, MD, of the Gustave Roussy Cancer Campus in Paris, France, presented results from a multicenter harmonization study that assessed Dako and Ventana PD-L1 assays for consistency.
“PD-L1 expression assessed by immunohistochemistry [IHC] is the main currently available predictive biomarker for the benefit of anti PD-1/PDL-1 treatments,” he said. “We need some harmonization of assays, and the development of laboratory tests should be studied because Dako and Ventana platforms are not available in all pathology laboratories.
Previous studies have shown that the 22C3, 28-8, and SP263 assays demonstrate close analytical performance with respect to tumor cell staining in non-small cell lung cancer (NSCLC), he said.
Dr Adam and colleagues evaluated results from PD-L1 Dako 22C3 and 28-8 assays, Ventana SP263 assays across multiple centers, and studied whether laboratory-developed tests (LDTs) could achieve comparable results to the assays in NSCLC.
The researchers stained a series of 41 tissue samples from patients with resected NSCLC with various levels of PD-L1 expression at 7 centers across France, using clones of 28-8, 22C3, SP263 and 2 other assays, E1L3N and SP142. For each matching platform, they performed 22C3, 28-8, and SP263 assays. For non-matching platforms and other antibodies, they used LDTs, which were designed in each center and harmonized based on tonsil tissue staining.
The researchers performed 35 stainings across different platforms and antibodies for each case. They scored PD-L1 staining for both tumor and immune cells.
28-8, 22C3 and SP263 assays were highly consistent for tumor cell and immune cell stainings across the 5 platforms. Among the 27 LDTs, 14 (51.8%) were consistent compared to reference assays and tumor cell staining.
SP263 had the highest consistency across all platforms for both immune and tumor cell stainings. Some LDTs showed a good correlation with only the 3 assays for tumor cells. There was low concordance for immune cell staining when the researchers used a 4-category scale with 1%, 5%, and 10% thresholds.
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“Our study revealed that caution is required for validation and further use of LDTs,” said Dr Adam. He added that selected LDTs will be validated on larger cohorts and by external quality assessment, the results of which will provide recommendations for PD-L1 testing in NSCLC.
- Adam J, Rouquette I, Damotte D, et al. Multicentric French harmonization study for PD-L1 IHC testing in NSCLC. Paper presented at: International Association for the Study of Lung Cancer 17th World Conference on Lung Cancer; December 2016; Vienna, Austria.