Immunohistochemical assays for programmed cell death ligand 1 (PD-L1) expression in non-small cell lung cancer (NSCLC) are either required or recommended to guide therapy with immune checkpoint inhibitors. Four commercially available immunohistochemical assays are currently available as either complimentary or companion diagnostic assay for their counterpart therapy. Harmonization or exchangeability of one assay for the other is a highly sought for goal. The aim of this study was to compare one assay, 22C3, with another, SP263, and examine whether they can be exchanged one for the other. Seventy samples from 70 patients with NSCLC were tested for PD-L1 using the SP263 and then the 22C3 antibody clones according to the manufacturer's instructions in case of the SP263 assay and according to a previously described and reported method for the 22C3 assay on the Ventana's ultra immunstainer. Results were evaluable in 51 cases, which were interpreted independently by 2 different pathologists on 2 different occasions for each case. The cases were given a percentage score based on the tumor proportion score. The Pearson correlation coefficient was calculated. A high concordance rate was found between the 2 assays. The Pearson correlation coefficient was 0.95, which indicates an almost perfect correlation (95% confidence limits, 0.92-0.97 and P<0.0001). The findings indicate that SP263 assay can be used in place of the 22C3 assay for PD-L1 assay in NSCLC, and it can be used on the Ventana platform.

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