First-line immunotherapy plus chemotherapy for ES-SCLC: Comparison between PD-1 and PD-L1 inhibitors in a real-world setting.

e20119 Background: PD-1/PD-L1 inhibitors in combination with platinum-etoposide (EP) based chemotherapy have been approved as first-line therapy in extensive-stage small cell lung cancer (ES-SCLC). However, whether PD-1 or PD-L1 inhibitors should be preferably selected is still undetermined. Methods: The retrospective study included 367 ES-SCLC patients who received standard first-line chemoimmunotherapy from 3 cancer centers in China from May 2018 to February 2023. The efficacy, including objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS) and overall survival (OS), as well as safety were evaluated between PD-1 and PD-L1 inhibitors. Results: Among 367 ES-SCLC patients, 80 received PD-1 inhibitors plus EP, and 287 received PD-L1 inhibitors plus EP as first-line treatment. The baseline characteristics between the two groups were well balanced. Although PD-L1 inhibitors had numerically higher ORR (66.2% vs. 56.3%, P = 0.114) and DCR (93.4% vs. 87.5%, P = 0.100) compared with PD-1 inhibitors, the difference were not statistically significant. We then observed similar PFS (7.5 m vs.7.7 m; HR = 0.9195% CI: 0.68–1.23, P = 0.547) and OS between groups. Further analysis revealed that combination of thoracic radiotherapy (TRT) with PD-1 or PD-L1 inhibitors showed similar efficacy. In addition, PD-1 or PD-L1 inhibitors had comparable efficacy in patients with different sites of metastasis. No additional immune-related adverse reactions (irAEs) were observed in the PD-1 inhibitor group compared with that in the PD-L1 inhibitor group (38.8% vs 39.7%, P = 0.875). Conclusions: PD-1 and PD-L1 inhibitors showed comparable efficacy and safety in the setting of first-line chemoimmunotherapy.