Tumor Mutational Burden and PD-L1 Expression in Non-Small-Cell Lung Cancer (NSCLC) in Southwestern China

Purpose: To explore the impact between the tumor mutational burden (TMB) and programmed death ligand-1 (PD-L1) expression on NSCLC in the Yunnan region of southwestern China. Patients and Methods: Seventy-one NSCLC specimens that were pathologically confirmed were collected at first. The TMB and driver genetic alterations were evaluated accordingly by next-generation sequencing (NGS). Afterwards, clinical parameters and tumor PD-L1 expressions were collected. Finally, the relationship between TMB, PD-L1 expression and clinical outcome was evaluated. Results: The median TMB was 5 (0.6-49) mutations/Mb by our NGS panel and the majority of patients (63/71, 88.7%) did not receive immunotherapy. The progression-free survival (PFS) was longer in TMB-low patients versus TMB-high ones (median 18.0 vs. 9.0 months, hazard ratio = 0.34, 95% confidence interval 0.14 to 0.84, p = 0.02) and the cut-off value was 10 mutations/Mb. The overall survival (OS) was longer in TMB-low patients vs. TMB-high ones (median 21.0 vs. 10.0 months, HR = 0.32, 95% CI 0.12 to 0.82, p = 0.02). Notably, our study also found that, excluding the eight patients with immunotherapy, the PFS was longer in patients with TMB-low vs. TMB-high (median 19.0 vs. 8.0 months, HR = 0.11, 95% CI 0.03 to 0.39, p < 0.01) and the OS was longer in TMB-low patients vs. TMB-high (median 21.0 vs 10.0 months, HR = 0.12, 95% CI 0.03 to 0.42, p < 0.01). Conclusion: TMB was a valid and independent prognostic biomarker for NSCLC patients' clinical outcome and comprehensive screening of TMB based on NGS is recommended for individualized treatment strategies in Yunnan population.