Cabozantinib and atezolizumab for recurrent or metastatic esophageal squamous cell carcinoma after platinum-based chemotherapy failure: a single-arm phase II study and biomarker analysis

PURPOSE: Anti-PD-1 immune-checkpoint inhibitors (ICIs) are approved for treating patients with recurrent or metastatic (R/M) esophageal squamous cell carcinoma (ESCC) who have failed platinum-based chemotherapy. However, their efficacy as monotherapy remains limited. We hypothesized that adding cabozantinib, a multikinase inhibitor with antiangiogenic and immunomodulatory properties, could enhance the therapeutic efficacy of atezolizumab, an anti-PD-L1 ICI, in patients with R/M ESCC. PATIENTS AND METHODS: A single-arm, single-institution phase II trial was conducted (NCT05007613) that included patients with ESCC who experienced disease progression following a platinum-based chemotherapy for R/M ESCC or within 6 months after chemo(radio)therapy for locoregional disease. Participants received cabozantinib 40 mg daily and atezolizumab 1200 mg every 3 weeks until disease progression or intolerable toxicity was reached. The primary endpoint was investigator-assessed objective response rate (ORR), and the secondary endpoints were progression-free survival (PFS), overall survival (OS), and toxicity profile. RESULTS: Between June 2021 and March 2024, 24 patients were enrolled in this study. With a median follow-up of 7.0 months (range, 0.5-38.1), 7 patients achieved partial responses and 7 had stable disease. The ORR was 29.1% (95% CI = 11.7%-60.1%), and the disease control rate (DCR) was 58.3% (95% CI = 31.9-97.9%). The median duration of response was 6.5 months (95% CI = 0.9-12.1), the median PFS was 2.2 months (95% CI = 0.64-3.76), and the median OS was 7 months (95% CI = 2.36-11.64). Of the 24 patients, 12 (50%) experienced ≥ grade 3 treatment-related adverse events. Patients with high PD-L1 expression and increased intratumoral or stromal CD8+ tumor infiltrating lymphocytes had numerically higher ORR and improved OS. CONCLUSION: The combination of cabozantinib and atezolizumab has an acceptable safety profile and moderate antitumor activity as a second-line treatment for patients with R/M ESCC.