Background and Importance In patients with NSCLC and programmed death ligand-1 (PD-L1) expression ≥50%, pembrolizumab as first-line treatment has shown an increase in survival over platinum-based chemotherapy. To date, it is not known whether higher PD-L1 expression is associated with longer survival.

Aim and Objectives The aim of this study is to evaluate the impact of PD-L1 expression levels on progression free survival (PFS) and overall survival (OS), in patients receiving first-line pembrolizumab treatment for NSCLC and its association to histologic type.

Material and Methods A retrospective analysis of patients with metastatic NSCLC and PD-L1 expression level of ≥50%, who were treated with pembrolizumab monotherapy as first-line therapy in our centre from January 2020 to January 2022 was carried out. The difference in response between the histologic type of NSCLC (adenocarcinoma and non-adenocarcinoma), and efficacy of pembrolizumab by level of PD-L1 expression was studied. ROC curve was used to evaluate the optimal PD-L1 cut-off point to identify a greater possibility of response. Event-time distributions were estimated using Kaplan–Meier methodology. Log-rank tests were used to test for differences in event-time distributions. All p-values are 2-sided and CIs are at the 95% level, with significance pre-defined to be at the 0.05 level.

Results 49 patients were included in the study. 36 patients (73.5%) had adenocarcinoma histology, 10 (20.4%) epidermoid, and 3 (6.1%) other. A cut-off of 80% for PD-L1 expression was established. 40 (81.6%) had PD-L1 expression <80% and 9 (18.4%) ≥80%. Median PFS was 14.7 months (95% CI: 7.0-15.1) in patients with PD-L1 <80% and 25.8 months (95% CI: not reached) in patients with PD-L1 ≥80% (p=0.017). No differences were found in OS. Patients with adenocarcinoma and PD-L1 expression ≥80% obtained better results in in terms of PFS: 19.3 months (95% CI: not reached, p=0.031).

Conclusion and Relevance Statistically significant differences in PFS but not OS were found in patients with NSCLC and PD-L1 ≥80% expression. Adenocarcinoma with PD-L1 ≥80% seem to benefit the most from pembrolizumab treatment than other NSCLC histologies. These findings could have implications for treatment selection based in NSCLC histology. Future research is needed.

References and/or Acknowledgements 1. Aguilar EJ et al., Outcomes to first-line pembrolizumab in patients with non-small-cell lung cancer and very high PD-L1 expression. AnnOncol.2019oct1;30(10):1653-1659.

Conflict of Interest No conflict of interest