PD-L1 Expression, Tumor Mutational Burden, and Combined Biomarker Prediction of Anti-PD-1 Response in Advanced Non-Small Cell Lung Cancer: A Prospective Multicenter Cohort

This study investigates combined PD-L1 TPS, tumor mutational burden, and CD8+ TIL density as composite biomarker predictors of anti-PD-1 objective response rate and progression-free survival in advanced NSCLC within the context of thoracic oncology and cancer immunotherapy, an area of growing scientific importance given its implications for pembrolizumab monotherapy patient selection, composite biomarker clinical assay development, and combination immunotherapy trial stratification. Using prospective cohort with pre-treatment tumor biopsy TMB-high/low (WES), PD-L1 TPS (22C3 IHC), CD8+ TIL density (IHC), and RECIST 1.1 response assessment at 9 weeks and every 12 weeks thereafter, we examine high PD-L1 TPS reflecting existing adaptive immune resistance from CD8+ T cell-mediated tumor recognition enabling anti-PD-1 reinvigoration, with TMB-high tumors generating neo-antigen load providing targets for reactivated T cells in 384 advanced NSCLC patients (248 adenocarcinoma, 136 squamous cell) with pre-treatment biopsy and pembrolizumab monotherapy, median follow-up 18.4 months drawn from 8 academic cancer centers across the Pacific Northwest and Western U.S. with centralized biomarker testing at Harborview Pathology. Results indicate that triple-positive (PD-L1 >=50%, TMB >=10 mut/Mb, CD8+ TIL high) group achieves ORR 68.4% and 12-month PFS 58.4% versus ORR 12.4% and 12-month PFS 18.4% in triple-negative; combined composite adds 0.12 AUC over PD-L1 alone (p < 0.001), with ORR 68.4% triple-positive vs. 12.4% triple-negative; AUC +0.12 composite vs. PD-L1 alone as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to thoracic oncology and cancer immunotherapy and carry actionable implications for the design of programs and policies targeting pembrolizumab monotherapy patient selection, composite biomarker clinical assay development, and combination immunotherapy trial stratification.