A randomized phase II study of toripalimab consolidation or observation after concurrent chemoradiotherapy in limited-stage small cell lung cancer.

8098 Background: In recent years, the use of immune checkpoint inhibitors has led to significant progress in the treatment of extensive-stage small cell lung cancer. However, there is limited data on the efficacy of immunotherapy in patients with limited-stage disease (LS-SCLC). Therefore, we conducted a phase II randomized study to verify the efficacy and safety of Toripalimab consolidation following definitive concurrent chemoradiotherapy (CCRT) in patients with LS-SCLC (ClinicalTrials.gov ID: NCT04418648). Methods: Patients with LS-SCLC who had achieved complete or partial response after definitive CCRT (including four to six cycles of etoposide and cisplatin , and curative-intent thoracic radiotherapy) were randomly assigned (1:1) to receive Toripalimab consolidation (240mg intravenously, every 3 weeks for 6 months) or observation. Prophylactic cranial irradiation (PCI) was recommended but not mandatory. The primary endpoint was progression-free survival (PFS) calculated from randomization, and secondary endpoints included overall survival (OS) and toxicity. Results: As of data cutoff (November 30, 2023), a total of 64 eligible patients (intent-to-treat population) were randomly assigned to the Toripalimab group (n = 31) or the observation group (n = 33), respectively. With the median follow-up of 25 months, PFS was significantly improved with Toripalimab (hazard ratio [95% CI]: 0.47 [0.22-1.02]; P = 0.04). The median PFS in observation group was 12.3 months (95% CI, 0.04-24.50), while the median PFS in the Toripalimab group has not been reached. The 24-month PFS rate was 61.6% (95% CI, 43.0%-88.3%) in the Toripalimab group and 34.8% (95% CI, 21.5%-56.3%) in the observation group. The 24-month OS was 82.7% (95% CI, 65.2%-100%; P = 0.23) in the Toripalimab group and 59.1%(95% CI, 44.2%-79.1%) in the observation group. There were 5(16.1%) and 3 (9.1%) patients in the Toripalimab group and observation group experiencing G2+ pneumonitis respectively. No G4+ toxic events occurred in either group. Conclusions: Our preliminary results suggested Toripalimab consolidation following definitive CCRT was effective and tolerable in LS-SCLC. Clinical trial information: NCT04418648 . [Table: see text]