Efficacy and safety of first-line PD-L1/PD-1 inhibitors in limited-stage small cell lung cancer: a multicenter propensity score matched retrospective study.

Abstract

The prognosis of small cell lung cancer (SCLC) patients is poor, and the standard first-line treatment for limited-stage small cell lung cancer (LS-SCLC) is still chemotherapy and thoracic radiotherapy. The primary objectives of our study were to confirm the superior efficacy of first-line immune checkpoint inhibitors (ICIs) plus etoposide and platinum (EP) for LS-SCLC and find crucial biomarkers. We analyzed LS-SCLC patients from three medical centers, employing propensity score matching for group comparability. Survival outcomes were estimated by Kaplan-Meier and Cox regression analyses. Additionally, we conducted univariate and multivariate analyses to investigate potential predictive factors. Among 150 patients in our study, we successfully matched 41 pairs. The median overall survival (OS) was 29.5 months in the EP + ICIs group and 20.0 months in the EP group {hazard ratio (HR) =0.64 [95% confidence interval (CI): 0.41-1.02], P=0.059}. The median progression-free survival (PFS) was significantly extended in the EP + ICIs group (14.6 months), compared to the EP group (8.6 months) [HR =0.42 (95% CI: 0.28-0.63), P<0.001]. After matching, patients receiving chemo-immunotherapy had a median OS of 36.1 months, significantly surpassing those receiving chemotherapy alone (19.0 months) [HR =0.51 (95% CI: 0.28-0.93), P=0.02]. And the patients in the EP + ICIs group also had longer PFS after matching [HR =0.42 (95% CI: 0.25-0.71), P=0.001]. No significant difference in the objective response rate (ORR) and treatment-related adverse events (trAEs) between the two groups was found (ORR: EP: 81.0%, EP + ICIs: 90.0%, P=0.14; trAEs: EP: grade 1-2, 49.3%; grade 3-4, 42.5%; EP + ICIs: grade 1-2, 40.0%; grade 3-4, 49.1%, P=0.62). The multivariate analysis presented that the history of immunotherapy [EP + PD-1 inhibitors: HR =0.33 (95% CI: 0.17-0.62), P=0.001; EP + PD-L1 inhibitors: HR =0.18 (95% CI: 0.06-0.60), P=0.005] and baseline lung immune prognostic index (LIPI) [intermediate: HR =2.22 (95% CI: 1.20-4.13), P=0.01; poor: HR =2.03 (95% CI: 0.71-5.77), P=0.18] were independent prognostic factors for PFS among all LS-SCLC cases. However, no independent prognostic factor was identified for OS. Our real-world data showed promising clinical efficacy and tolerable safety of first-line programmed cell death protein 1 (PD-1) inhibitors or programmed cell death ligand 1 (PD-L1) inhibitors in cases with LS-SCLC. Additionally, LIPI may serve as a valuable prognostic factor.