PL04a.04: Multicentric French Harmonization Study for PD-L1 IHC Testing in NSCLC

Abstract

PD-L1 immunohistochemistry (IHC) is considered as a predictive biomarker for most anti PD-1/PDL-1 therapies in non-small cell lung cancer, but different assays were used in clinical trials. Several studies have compared 4 assays (22C3, 28-8, SP142, SP263) performed in central laboratories on dedicated platforms. In order to harmonize and make PD-L1 testing widely available on most IHC platforms and centers, we compared PD-L1 Dako (22C3, 28-8) and Ventana (SP263) assays and laboratory-developed tests (LDT). IHC with five anti-PD-L1 clones (28-8, 22C3, E1L3N, SP142 and SP263) was performed concomitantly on 41 NSCLC surgical specimens in 7 centers. The IHC platforms used were Ventana BenchMark Ultra (2 centers), Leica Bond (2 centers) or Dako Autostainer Link 48 (3 centers). For each matching platform, 22C3, 28.8 and SP263 assays were performed. For non-matching platforms and other antibodies, LDT were developed in each center and harmonized based on tonsil tissue staining. A total of 35 stainings were performed across different platforms and antibodies for each case. Seven thoracic pathologists trained to PD-L1 scoring in expert courses participated. Each pathologist analyzed 6 cases and compared the stainings obtained with the 5 antibodies on all platforms. Tumor cell and immune cell D-L1 stainings were scored semi-quantitatively as recommended in PD-L1 Dako and Ventana assays. For statistical analysis, 1, 5, 25, 50% and 1, 5, 10% thresholds were used for tumor cells and immune cells, respectively. 28-8, 22C3 and SP263 assays were highly concordant for tumor cell and immune cell stainings across the 5 Dako or Ventana platforms (R2=0.886 to 0.953). LDT demonstrated various levels of concordance as compared to those 3 assays. Notably, LDT using SP263 clone were the most concordant across all platforms for both immune cell and tumor cell stainings, whereas some selected LDT with clones 28-8, 22C3 and E1L3N, but not SP142, showed a good correlation with the 3 assays regarding tumor cells only. 28-8, 22C3 and SP263 assays gave comparable results across dedicated platforms for tumor cells staining, as well as some selected LDT protocols using 28-8, 22C3, SP263 and E1L3N clones. These results will be further validated at the national level in order to provide recommendations for the use of assays and LDT for PD-L1 testing in NSCLC.