the goal of the cLoVeR study was to perform a pairwise comparison of four tests based on the same patient population with non-small cell lung cancer (NSCLC): three validated PDL1 immunohistochemistry (IHC) assays (Ventana SP142, Ventana SP263, Dako 22C3) and one PCR test. Four hundred seventy-three NSCLC samples were obtained from a biobank and were stained using PDL1 IHC assays. Four trained pathologists independently evaluated the percentage of tumor cells (TC) and immune cells (IC) that stained positive at any intensity. PDL1 transcripts were quantified in 437 patients by a standard Taqman RT-PCR assay using SDHA as a reference gene. A concordance analysis was performed to assess (1) the correlation of TC and IC between different assays and (2) the predictive properties of one test for another. "High" RNA expression was detected in 187 of 437 (43%) patients. The percentage of PDL1-positive cells (≥1%) was higher among the IC than the TC in all IHC three assays. The Pearson correlation coefficients (PCC) for TC were 0.71, 0.87, and 0.75 between 22C3/ SP142, 22C3/SP263, and SP263/SP142, respectively. The PCC for IC were 0.45, 0.61, and 0.68 for the same pairs. A low correlation was observed between the PCR test and each of the three IHC assays; however, if a patient tested low/negative by PCR, then they were likely to test negative by any single IHC test with a high probability (92-99%). Among patients who tested positive by PCR, only 9-45% tested positive by IHC assays. There was excellent positive and negative agreement (>91%) between 22C3 and SP263 staining using the recommended individual cutoffs for first-line treatment. PCR RNA expression analysis is not equivalent to IHC. However, this method may have some potential for the identification of PDL1-negative tumors. 22C3 could be considered as a substitute for SP263 in first-line treatment.In recent years, immune checkpoint inhibitors targeting programmed cell death 1 (PD-1) or programmed cell death ligand 1 (PDL1, CD274), have presented an alternative revolutionary therapeutic approach for patients with nonsquamous and squamous non-small-cell lung cancer (NSCLC) 1 .Pembrolizumab, an anti-PD-1 humanized antibody, is recommended as a first-line single agent for patients with metastatic NSCLC and PDL1 expression levels greater than 50% detected by immunohistochemistry (IHC) with the diagnostic antibody 22C3 (Agilent) 2,3 . Pembrolizumab was recently approved for use in the first-line One test-specific cutoff rule for each assay was pre-specified as: for first-line treatment the Tumor Proportion Score (TPS, the percentage of viable tumor cells showing partial or complete membrane staining relative to all viable tumor cells present in the sample) ≥50% for 22C3, TC or IC ≥ 5% for SP142, TC ≥ 25% for SP263, and for second-line treatment TPS ≥ 1% for 22C3, TC ≥ 50% or IC ≥ 10% for SP142, and TC ≥ 25% for SP263 (Table 1). Delta CT = 2 was conditionally chosen as the threshold between "high" ("positive") and "low/absent" ("negative") PDL1 RNA expression.
ResultsPatie...