P2.09-21 A Prospective Study of the Concordance for PD-L1 Status in Core Needle Biopsy and Corresponding Resection Specimen in NSCLC

Some studies have demonstrated a relatively poor concordance of PD-L1 IHC expression between biopsies and corresponding resection specimens. To address this central and relevant issue having a significant impact on treatment stratification for patients with NSCLC, we evaluated a novel method to compare and evaluate PD-L1 status in biopsies and resection samples. Randomly core needle aspiration biopsy was performed in 170 resected NSCLC samples with 1 to 2 biopsies per centimeter in longest diameter of tumor. Among these 170 cases, a total of 52 cases were selected for the study. 41 cases were characterized as PD-L1 positive as a PD-L1 TPS≥ 1%), 1 case which the TPS<1% resected specimen with obvious stained tumor area and randomly 10 specimens being PD-L1 negative. In total 221 biopsies were available for the 52 resection cases. The PD-L1 expression in resected specimens and corresponding biopsies were evaluated by the PD-L1 IHC 22C3 pharmDx assay (Agilent) on the Dako Autostainer. In our investigation, the concordance of PD-L1 status in biopsy and resection was not influenced by number of tumor cells at 1% and 50% cut-off’s. The length of biopsy improves concordance of PD-L1 status but is not statistically significant (table 1). In figure 1. under 1% cut-off, the PD-L1 status in biopsy and resection is concordant irrespective of biopsies density, whereas the density of biopsies improves the concordance for 50% cut-off. The threshold was 1 per centimeter in longest diameter of tumor.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The concordance between biopsy and resected specimen is related to the length, density of biopsy and the clinical cutoff. Increasing the biopsy density will improve accuracy of PD-L1 detection.