JCO Glob Oncol. 2020 Jul;6:1218-1224. doi: 10.1200/GO.20.00107.
PURPOSE: Programmed death-ligand 1 (PD-L1) is a marker for checkpoint inhibitor use in the management of solid tumors, especially in non-small-cell lung cancer (NSCLC). Our study was aimed at determining the patterns of PD-L1 expression and cluster of differentiation 8 (CD8) immunostains in patients with NSCLC in the Arab population.
METHODS: Archival tumor tissue from patients with a confirmed diagnosis of NSCLC were obtained and stained for PD-L1 with antibody 22C3, using immunohistochemistry staining and giving the tumor proportion score (TPS) as a percentage from 0%-100% of stained tumor cells. Tumors were categorized into negative expressers (TPS < 1%), low positive (TPS, 1%-49%), and high positive (TPS, 50%-100%). Correlation of expression with clinical and pathologic features, including CD8-positive (CD8+) lymphocyte density, was also analyzed.
RESULTS: Two hundred patients with NSCLC were included in the study from 6 centers in Saudi Arabia and Algeria. Median age was 65 years (28-93 years), and the majority were men (75%) with stage 4 NSCLC (64%). The TPS was high in 37 patients (18%), low in 60 patients (30%), and negative in 103 patients (52%). In a univariate analysis, the following were significant predictors of any PD-L1 expression (> 1%): male sex, being Saudi national patients, high expression of CD8+, and presence of tumor-infiltrating lymphocytes. In the multivariate analysis, only high expression of CD8+ cells (≥ 2+) was significant, with an odds ratio of 4.4 (95% CI, 1.5 to 12.9; P = .003).
CONCLUSION: PD-L1 expression in our population is similar to the published literature and correlated with the density of CD8+ cells. Validation of the predictive value of this marker in our population and identifying easier and reliable methods to test for it are warranted.