Efficacy and safety comparison of PD-1 inhibitors vs. PD-L1 inhibitors in extensive-stage small-cell lung cancer: a retrospective comparative cohort study

BACKGROUND: Evidence from clinical research and meta-analyses have suggested that programmed cell death 1 (PD-1) inhibitors and programmed cell death ligand 1 (PD-L1) inhibitors plus chemotherapy could achieve a significant survival benefit for extensive-stage small-cell lung cancer (ES-SCLC) patients. However clinical researches concerned about the comparation between the PD-1 and PD-L1 inhibitors were relatively lacking. METHODS: We collected the data of ES-SCLC patients treated with PD-1 inhibitors or PD-L1 inhibitors. The primary endpoints were overall survival (OS) and progression-free survival (PFS). Secondary endpoint included adverse events (AEs). RESULTS: The data of 221 ES-SCLC patients treated with PD-1 (n=146) or PD-L1 inhibitors (n=75) between February 2017 and June 2020 were retrospectively collected. The median OS (mOS) and median PFS (mPFS) were 19.07 and 8.27 months, respectively, in patients treated with PD-1 inhibitors. In the PD-L1 group, mOS has not been reached, and mPFS was 7.95 months. No significant differences were observed between the 2 groups in OS [hazard ratio (HR), 1.472; 95% confidence interval (CI), 0.847–2.220; P=0.198] and PFS (HR, 0.816; 95% CI, 0.577–1.155; P=0.251). The rates of patients showed AEs of any grade treated with PD-1 or PD-L1 were 67.12% and 64.00%, with no significant difference (P=0.642, χ(2)=0.216), ≥3 grade AEs occurred in 42 (28.76%) and 16 (21.33%) patients treated with PD-1 and PD-L1 inhibitors separately, also no significant difference (P=0.234, χ(2)=1.415) was observed. According to subgroup analysis, camrelizumab revealed a longer mPFS (15.17 months) compared with other immune-checkpoint inhibitors (ICIs). PD-1 and PD-L1 inhibitors revealed comparable efficacy in ES-SCLC patients with brain metastases, with no significant differences in OS (HR, 1.505; 95% CI, 0.684–3.311; P=0.309) and PFS (HR, 0.649; 95% CI, 0.356–1.182; P=0.157). CONCLUSIONS: PD-1 and PD-L1 inhibitors might achieved comparable survival benefit and safety in ES-SCLC patients. A longer PFS was observed in patients treated with PD-1 inhibitors in the first-line treatment, and the PD-1 inhibitor camrelizumab might have achieved a better PFS compared with other ICIs.