PD-L1 phenotype classification based on expression in tumor and immune cells as a potential biomarker for optimizing anti-PD-1/CTLA-4 immunotherapies in NSCLC.

BACKGROUND: Compared with conventional chemotherapy, pembrolizumab-based chemoimmunotherapy (Pembro) and nivolumab plus ipilimumab with or without two cycles of platinum-doublet chemotherapy (Nivo+Ipi) improve survival in advanced non-small cell lung cancer (NSCLC). However, biomarkers for selecting optimal immunotherapy remain unclear. This study aimed to assess whether programmed cell death-ligand 1 (PD-L1) expression on tumor and immune cells (ICs) can guide first-line immunotherapy in advanced NSCLC. METHODS: This multicenter, observational study retrospectively reviewed patients with NSCLC treated with first-line Pembro or Nivo+Ipi who had evaluable PD-L1 expression on tumor (Tumor Proportion Score (TPS), 22C3) and ICs score (SP142). In addition, whole-exome and RNA sequencing were performed on treatment-naïve NSCLCs with available PD-L1 expression status by both assays. RESULTS: Between 2019 and 2023, 198 patients were included (Pembro/Nivo+Ipi: 137/61). In the Pembro cohort, patients with high TPS (≥ 50%) had significantly longer progression-free survival (PFS) than those with low TPS (< 50%) (median PFS (mPFS, months): 8.1 vs 7.1; p=0.02), while IC score was not predictive. In the Nivo+Ipi cohort, high IC score (≥1) was associated with longer PFS than low IC score (0) (mPFS: 7.7 vs 2.8; p=0.04), while TPS showed no impact. Among patients with low TPS/high IC scores, Nivo+Ipi achieved longer PFS than Pembro (mPFS: 12.4 vs 6.6; restricted mean survival time (RMST)(Nivo+Ipi)/RMST(Pembro) (24 months)=1.5; p=0.049). Multiomics analysis using 152 NSCLC samples showed that tumors with low TPS/high IC scores exhibited an activated tumor immune microenvironment comparable to that of tumors with high TPS. However, these tumors had significantly highest tumor mutation burden (TMB) and regulatory T cell (T(reg)) fraction among the PD-L1 phenotypes (median TMB (mut/Mb): 1.6 in tumors with low TPS/low IC score, 18.2 in low TPS/high IC score, and 1.9 in high TPS/any IC score; median T(reg) fraction (×10(-2)]: 0.0, 0.2, and 0.0, respectively), supporting a potential benefit of cytotoxic T-lymphocyte-associated antigen 4 blockade in addition to programmed cell death protein 1 (PD-1)/PD-L1 inhibition in this subgroup. CONCLUSIONS: Patients with NSCLC and low TPS/high IC scores may benefit more from Nivo+Ipi than from Pembro due to distinct genomic and immunological features, including high TMB and T(reg) fraction.