Clinicopathologic correlates of first-line pembrolizumab effectiveness in patients with advanced NSCLC and a PD-L1 expression of ≥ 50

Background: Single-agent pembrolizumab represents the standard first-line option for metastatic non-small-cell lung cancer (NSCLC) patients with a PD-L1 (programmed death-ligand 1) expression of ≥ 50%. Methods: We conducted a multicenter retrospective study aimed at evaluating the clinicopathologic correlates of pembrolizumab effectiveness in patients with treatment-naïve NSCLC and a PD-L1 expression of ≥ 50%. Results: One thousand and twenty-six consecutive patients were included. The objective response rate (ORR) was 44.5% (95% CI 40.2–49.1), while the median progression free survival (PFS) and overall survival (OS) were 7.9 months (95% CI 6.9–9.5; 599 events) and 17.2 months (95% CI 15.3–22.3; 598 censored patients), respectively. ECOG-PS ≥ 2 (p < 0.0001) and bone metastases (p = 0.0003) were confirmed to be independent predictors of a worse ORR. Former smokers (p = 0.0002), but not current smokers (p = 0.0532) were confirmed to have a significantly prolonged PFS compared to never smokers at multivariate analysis. ECOG-PS (p < 0.0001), bone metastases (p < 0.0001) and liver metastases (p < 0.0001) were also confirmed to be independent predictors of a worse PFS. Previous palliative RT was significantly related to a shortened OS (p = 0.0104), while previous non-palliative RT was significantly related to a prolonged OS (p = 0.0033). Former smokers (p = 0.0131), but not current smokers (p = 0.3433) were confirmed to have a significantly prolonged OS compared to never smokers. ECOG-PS (p < 0.0001), bone metastases (p < 0.0001) and liver metastases (p < 0.0001) were also confirmed to be independent predictors of a shortened OS. A PD-L1 expression of ≥ 90%, as assessed by recursive partitioning, was associated with significantly higher ORR (p = 0.0204), and longer and OS (p = 0.0346) at multivariable analysis. Conclusion: Pembrolizumab was effective in a large cohort of NSCLC patients treated outside of clinical trials. Questions regarding the effe