Comparison of PD-L1 immunohistochemistry assays and response to PD-1/L1 inhibitors in advanced non-small-cell lung cancer in clinical practice.

AIMS: Several studies have demonstrated analytical comparability between different PD-L1 assays, but their clinical validity in non-small-cell lung cancer in terms of response to treatment outside clinical trials has not been established. The aim of our study is to assess the analytical performance of laboratory-developed tests for Ventana SP263 and Agilent/Dako 22C3, and to investigate the association between PD-L1 assays and response to PD-1/L1 inhibitors. METHODS AND RESULTS: PD-L1 SP263 and 22C3 assays were performed on 302 consecutive non-small-cell lung carcinoma samples Both assays were optimised for use on the automated Ventana BenchMark Ultra platform. Scoring algorithms for staining of the tumour cells using the established cut-offs were applied to all samples. Best overall response (BOR) for 44 patients treated with either nivolumab, pembrolizumab or atezolizumab were assessed using recist version 1.1 and correlated with PD-L1 assay results. Assays showed good agreement, with a concordance correlation coefficient of 0.86 [95% confidence interval (CI) = 0.82-0.90)]. Comparing the assays using cut-offs of 1%, 5%, 10%, 1-49% and ≥50% showed an association between the two assays (P < 0.0001). The SP263 10% cut-off (P = 0.032) was associated with BOR, whereas the 1% (P = 0.087) and 5% (P = 0.051) cut-offs were not. In contrast 22C3, cut-offs of 1% (P = 0.019), 5% (P = 0.025) and 10% (P = 0.014) were all associated with BOR. CONCLUSIONS: The SP263 and 22C3 LDTs demonstrated good analytical concordance, and correlation with response to PD-1/L1 inhibitors.

PD-L1 Testing in Guiding Patient Selection for PD-1/PD-L1 Inhibitor Therapy in Lung Cancer.

Immunotherapy with programmed death 1 (PD-1)- and programmed death-ligand 1 (PD-L1)-targeted monoclonal antibodies has dramatically changed the therapeutic and prognostic landscape for several types of malignancy. PD-1 and PD-L1 are immune checkpoint proteins whose binding ultimately result in T cell exhaustion and self-tolerance. Blocking this pathway 'releases the brakes' on the immune system and allows for attack of tumor cells that express PD-L1. The clinical trials that led to the US Food and Drug Administration (FDA) approval of these agents used different immunohistochemical (IHC) platforms with various PD-L1 antibodies to assess for PD-L1 expression on either tumor cells or tumor-infiltrating immune cells. There are four PD-L1 IHC assays registered with the FDA, using four different PD-L1 antibodies (22C3, 28-8, SP263, SP142), on two different IHC platforms (Dako and Ventana), each with their own scoring systems. Attempts at harmonization of PD-L1 IHC antibodies and staining platforms are underway. While PD-L1 IHC can be used to predict the likelihood of response to anti-PD-1 or anti-PD-L1 therapy, a proportion of patients that are negative can have a response and identification of alternative biomarkers is critical to further refine selection of patients most likely to respond to these therapies.