Comparative analysis of first-line treatment in NSCLC including unresectable stage III (IIIB/IIIC) and stage IV with low PD-L1 expression: Clinical trial eligible versus ineligible patients

Background: Clinical trial eligible patients with advanced non-small cell lung cancer (aNSCLC) and low programmed cell death ligand 1 (PD-L1) expression achieve greater benefit from immune checkpoint inhibitor (ICI) combination chemotherapy (ICI-Chemo) compared with Chemo alone. We examined whether patients ineligible for clinical trials may benefit from ICI-Chemo. Methods: This multicenter retrospective cohort study enrolled patients with aNSCLC, including unresectable Stage III (IIIB/IIIC) and IV disease with a PD-L1 tumor proportion score of 1–49% treated with ICI-Chemo or Chemo as first-line therapy from 2018 to 2023 in Japan. Treatment outcome and safety of ICI-Chemo versus Chemo groups in trial-eligible and trial-ineligible patients was compared based on criteria from previous phase III clinical trials. Results: Overall, 728 patients were analyzed: 333 trial-eligible and 395 ineligible patients. The median overall survival was 25.1 months in the ICI-Chemo group and 18.5 months in the Chemo group for eligible patients (HR 0.73, 95 %CI: 0.54–0.97) and was 18.2 months in the ICI-Chemo group and 14.9 months in the Chemo group for ineligible patients (HR 0.75, 95 %CI: 0.59–0.95). Median progression-free survival was longer with ICI-Chemo in both groups. For ineligible patients, performance status (PS) ≥ 2 and squamous cell carcinoma (SqCC) were clinical factors associated with worse survival prognosis, and survival outcomes with ICI-Chemo and Chemo were comparable. The ineligible group had no increase in severe adverse events compared to the eligible group. Conclusions: This study suggests a possible clinical benefit of receiving ICI-Chemo for trial-ineligible patients with low PD-L1 expression, excluding those with PS ≥ 2 or SqCC.