PD-1 inhibitor monotherapy versus combination therapy: A real-world study of patients with recurrent or metastatic advanced esophageal squamous cell carcinoma after first-line chemotherapy

Context: Although programmed death 1 (PD-1) inhibitors are a standard second-line treatment for esophageal squamous cell carcinoma (ESCC), their efficacy when used in combination with chemotherapy or anti-angiogenesis targeted therapy is unclear. Aim: To compare the efficacy and safety of PD-1 inhibitor monotherapy with that of combination therapy. Setting and Design: A retrospective study was conducted at the Shandong Cancer Hospital. Materials and Methods: Based on records, patients with advanced ESCC, treated with second-line or above PD-1 inhibitor-containing regimens from August 15, 2019 to April 12, 2021 were divided into combination (PD-1 inhibitors plus chemotherapy or anti-angiogenesis targeted therapy) and monotherapy groups. The primary endpoints were progression-free survival (PFS) and overall survival (OS). Statistical Analysis Used: The baseline differences between subgroups were assessed using the χ2-test, Fisher's exact test, or Student's t-test. Follow-up period, PFS, OS, median survival, and 95% confidence intervals (CIs) were estimated using Kaplan‒Meier analysis. The log-rank test was used to compare subgroups. Results: In the 169 patients included, clinical features were well balanced between both groups. The median PFS of the combination group was better than that of the monotherapy group (8.5 months [95%CI 6.3-10.7] vs. 3.2 months [95%CI 0.0-6.5]; hazard ratio (HR) = 0.34 [95%CI 0.13-0.92]; P < 0.001). The median OS showed the same trend (18.9 months [95%CI 14.4-23.3] vs. 9.8 months [95%CI 6.3-13.2]; HR = 0.47 [95%CI 0.21-1.04]; P = 0.010). Conclusion: Using PD-1 inhibitors in a combination treatment may improve PFS and OS, with acceptable toxicities.