Abstract
BACKGROUND: Esophageal squamous cell carcinoma (ESCC) has a poor prognosis, with limited second-line systemic therapy options, and represents an increasing disease burden in Japan. In the phase 3 RATIONALE-302 study, the anti-programmed cell death protein 1 antibody, tislelizumab, significantly improved overall survival (OS) versus chemotherapy as second-line treatment for advanced/metastatic ESCC. Here, we report the Japanese patient subgroup results. METHODS: Patients with advanced/metastatic ESCC, with disease progression during/after first-line systemic therapy were randomized 1:1 to open-label tislelizumab 200 mg every 3 weeks or investigator's choice of chemotherapy (paclitaxel/docetaxel). Efficacy and safety were assessed in all randomized Japanese patients. RESULTS: The Japanese subgroup comprised 50 patients (n = 25 per arm). Tislelizumab improved OS versus chemotherapy (median: 9.8 vs. 7.6 months; HR 0.59; 95% CI 0.31, 1.12). Among patients with programmed death-ligand 1 score ≥ 10%, median OS was 12.5 months with tislelizumab (n = 10) versus 2.9 months with chemotherapy (n = 6) (HR 0.31; 95% CI 0.09, 1.03). Tislelizumab improved progression-free survival versus chemotherapy (median: 3.6 vs. 1.7 months, respectively; HR 0.50; 95% CI 0.27, 0.95). Objective response rate was greater with tislelizumab (32.0%) versus chemotherapy (20.0%), and responses were more durable (median duration of response: 8.8 vs. 2.6 months, respectively). Fewer patients experienced ≥ grade 3 treatment-related adverse events with tislelizumab (24.0%) versus chemotherapy (47.8%). Tislelizumab demonstrated an improvement in health-related quality of life versus chemotherapy. CONCLUSIONS: As second-line therapy for advanced/metastatic ESCC, tislelizumab improved OS versus chemotherapy, with a favorable safety profile, in the Japanese patient subgroup, consistent with the overall population. CLINICAL TRIAL REGISTRY: ClinicalTrials.gov: NCT03430843.