Clinicopathologic Correlation With Expression of PD-L1 on Both Tumor Cells and Tumor-infiltrating Immune Cells in Patients With Non–Small Cell Lung Cancer

Our study was to evaluate the concordance of programmed cell death-ligand 1 (PD-L1) expression between 22C3 and SP263 assay and explore the association of clinicopathologic features with expression of PD-L1 on both tumor cells (TC) and tumor-infiltrating immune cells (IC). We retrospectively assessed the PD-L1 expression in 305 patients with lung adenocarcinoma or adenosquamous carcinoma by 22C3 and SP263 assay. The association of PD-L1 expression by 22C3 assay with clinicopathologic features was also analyzed. The prevalence of PD-L1 expression by 22C3 assay was 20.7% with a ≥50% cutoff and 46.6% with a ≥1% cutoff. The concordance rates between 2 PD-L1 assays while using 1%, 5%, 25%, and 50% positive TC as the cutoffs were 91.8%, 93.1%, 95.1% and 99.0%, respectively. For PD-L1 expression on IC, the concordance rate was 93.4% using a 1% cutoff. According to the results of 22C3 assay, high PD-L1 expression (using a ≥50% cutoff) on TC was significantly associated with smoking, advanced stage disease, and KRAS mutation. PD-L1 expression on IC was significantly associated with smoking and KRAS mutation. PD-L1 expression on TC and IC were both significantly associated with average number of cigarettes smoked ≥20 per day. The 22C3 and SP263 assays were highly concordant for assessment of PD-L1 expression on TC and IC. Patients with KRAS mutation and smoking history, particularly those having a large number of cigarettes smoked per day, were more likely to have PD-L1 expression on both TC and IC.