Programmed cell death ligand 1 (PD-L1) inhibitors versus programmed cell death 1 (PD-1) inhibitors for the first-line therapy of extensive-stage small cell lung cancer: A propensity score-matched study.

206 Background: Addition of programmed cell death ligand 1 (PD-L1) inhibitors or programmed cell death 1 (PD-1) inhibitors to etoposide‐platinum (EP) chemotherapy has become the standard first-line regimen for ES-SCLC. The clinical efficacy and safety between the two types of immune checkpoint inhibitors (ICIs) remain controversial. We conduct the retrospective study and propensity score-matched analysis to explore the potential differences between them. Methods: Patients diagnosed with ES-SCLC and treated by EP plus PD-L1 or PD-1 inhibitors at Shandong Cancer Hospital between March 2019 and November 2022 were reviewed retrospectively. According to PD-L1 or PD-1 inhibitors, they were divided into two groups. Propensity score matching (1:1) was performed to balance the baseline characteristics of the two groups. The baseline characteristics and adverse events between the two groups were compared using the chi-squared test. The survival curves of overall survival (OS) and progression-free survival (PFS) were plotted by the Kaplan-Meier method and differences were analyzed by the log-rank test.The primary endpoints were OS and PFS. Results: As a result, 448 patients were analyzed in this study. 264 patients received PD-L1 inhibitors plus EP and 184 received PD-1 inhibitors plus EP. The median follow-up was 17.6 months. The median OS and PFS was 20.4 months and 7.8 months in the overall population. Before propensity score matching, the median OS was 20.1 months in PD-L1 inhibitor plus EP group and 20.7 months in PD-1 inhibitor plus EP group, respectively (HR 1.043, 95%CI 0.776-1.401; p= 0.781). The median PFS was 7.6 months in the PD-L1 inhibitor plus EP group and 8.5 months in PD-1 inhibitor plus EP group (HR 1.099, 95%CI 0.886-1.364; p= 0.390). After propensity score matching, the median OS and PFS were 20.4 months and 7.8months in PD-L1 inhibitor plus EP group, and those were 20.1 months and 8.6 months in PD-1 inhibitor plus EP group. There was no significant difference in OS and PFS between PD-L1 inhibitors plus EP and PD-1 inhibitors plus EP in the matched population (HR 1.104; p= 0.578 and HR 1.072; p= 0.602, respectively). The overall adverse events were comparable in the two groups. Only ≥3 grade neutropenia was more frequent in the PD-L1 inhibitors plus EP group (77.7% vs 69.0%, p= 0.040). Conclusions: In conclusion, the overall efficacy and safety profile was similar between PD-L1 inhibitors and PD-1 inhibitors for the first-line treatment of ES-SCLC.