Heterogeneity of Tumor and Immune Cell PD-L1 Expression and Lymphocyte Counts in Surgical NSCLC Samples

© 2017 Elsevier Inc. Expression of programmed death-ligand 1 (PD-L1) in tumor cells and infiltrating immune cells was retrospectively analyzed in a cohort of surgically-treated patients with non–small-cell lung cancer. There was significant discordance of PD-L1 expression between different tumor areas, especially in the immune cell compartment. Heterogeneous PD-L1 expression represents a challenge for adequate biomarker-based selection of patients for programmed cell death protein 1/PD-L1-directed therapies. Background Immune-checkpoint inhibitors against programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) have shown remarkable therapeutic activity in non–small-cell lung cancer (NSCLC). However, biomarker-based patient selection remains a challenge. Our aim was to assess the heterogeneity of various immune markers between different tumor areas of surgically resected NSCLC specimens. Materials and Methods We included 94 adenocarcinoma (ADC) and 50 squamous cell carcinoma (SCC) specimens. Two distinct tumor areas of each tumor sample were selected and incorporated into tissue microarrays. PD-L1 expression in tumor cells (TCs) and immune cells (ICs) was assessed using clone SP142 (Ventana). PDL1 gene amplification was assessed using fluorescence in situ hybridization. CD3 and CD8 densities were quantified using digital image-based analysis. Heterogeneity was assessed using kappa agreement index (KI) and intraclass correlation coefficient. Results Prevalence of PD-L1 expression was 16.8% in TCs and 27.8% in ICs. Eleven tumors (7.6%) showed PDL1 amplification. In ADC, KI of PD-L1 TC and IC expression between cores was 0.465 and 0.260, compared with 0.274 and 0.124 in SCC, respectively. Higher concordance was observed for PDL1 amplification (KI, 0.647 in ADC and KI, 1 in SCC). Eleven (61.1%) of 18 amplified cores showed PD-L1 staining in < 5% of TCs. Intraclass correlation coefficients for CD3 and CD8 were 0.293 and 0.186 in ADC and 0.489 and 0.610 in SCC samples, respectively. Conclusions We found significant heterogeneity of PD-L1 expression in both ADC and SCC samples, especially in the IC compartment. Heterogeneous expression of PD-L1 could misclassify patients for PD-1/PD-L1-directed therapies.