Programmed Death Ligand 1 Expression in Paired Non-Small-Cell Lung Cancer Tumor Samples

We measured programmed death ligand 1 (PD-L1) expression in paired tumor tissue samples collected at different dates and lesions from 91 patients with nonesmall cell lung cancer. There was a statistically significant correlation in PD-L1 scores, with a 67% concordance rate when samples were categorized as PD-L1 positive and PD-L1 negative. These findings should be considered when selecting patients for clinical trials or treatment on the basis of PD-L1 expression. Background: Programmed death ligand 1 (PD-L1) expression may predict response to antieprogrammed death 1 (antiePD-1) or antiePD-L1 treatment. There is limited information on changes in PD-L1 expression over time in patients with nonesmall cell lung cancer (NSCLC). Patients and Methods: Eligible patients with NSCLC who received surgery or underwent biopsy at Samsung Medical Center, Seoul, Republic of Korea, and Aarhus University Hospital, Aarhus, Denmark, between February 2004 and April 2012 were included. PD-L1 expression in paired tumor tissue samples from the same patients at different dates and lesions was measured using a laboratory-developed prototype immunohistochemistry assay (22C3 antibody). PD-L1 positivity was defined as tumor cell membrane positivity in > 1% of tumor cells (proportion score). Concordance of PD-L1 expression was analyzed by treating proportion score as categoric or continuous variables. Results: Ninety-one patients were included in the analysis. The median interval between the 2 tumor collection dates was 20 months, with 91% of paired samples collected > 3 months apart. The concordance rate for PD-L1 classification between paired samples was 67% (95% confidence interval, 57%-77%). When treating the immunohistochemistry proportional score as a continuous variable, a significant correlation of PD-L1 expression was observed between the paired samples (Pearson correlation coefficient, 0.61; P < .001). Conclusion: There are good correlations of PD-L1 expression from paired NSCLC samples. For patients whose PD-L1 status is negative, it may be valuable to obtain additional tissue samples for retesting PD-L1 expression when antiePD-1 immunotherapy is considered.