IL-21 and IL-33 May Be Effective Biomarkers to Predict the Efficacy of PD-1 Monoclonal Antibody for Advanced Cholangiocarcinoma

Background and Objective: Treatment options for patients with advanced biliary tract cancer (BTC) are limited. The programmed cell death protein-1 (PD-1) inhibitors may have synergistic effects with chemotherapy. Therefore, the aim of our study was to provide real-world data on treatment outcomes in BTC patients receiving chemotherapy alone versus a combination of chemotherapy and PD-1 inhibitors. Additionally, we explored potential markers predictive of PD-1 inhibitor efficacy in this combined therapy. Methods: We conducted a review of patients at Changzhou First People's Hospital who received PD-1 inhibitors in combination with chemotherapy or chemotherapy alone as first-line treatment for advanced BTC. The primary endpoints of the study were progression-free survival (PFS) and overall survival (OS). Kaplan-Meier survival curves and the log-rank test were used to analyze the data. Immunohistochemistry showed the expression of interleukin-21 (IL-21), interleukin-33 (IL-33), and Eomes in the tumor tissue of patients who received PD-1 inhibitors in combination with chemotherapy. Results: The study enrolled 61 patients receiving PD-1 inhibitors combined with chemotherapy and 65 receiving chemotherapy alone. The median OS and PFS for patients receiving PD-1 inhibitors in combination with chemotherapy were 11.7 and 6.7 months, respectively. These durations were significantly longer than those for chemotherapy alone: OS of 10.3 months (95% CI: 0.16-0.21, p = 0.031) and PFS of 5.3 months (95% Confidence interval (CI) 0.25-0.32, p = 0.018). High IL-21 expression or low IL-33 expression in tumor tissue correlated with better response rates to chemotherapy combined with PD-1 inhibitors. Conclusions: Combining PD-1 inhibitors with chemotherapy shows good antitumor activity, making it an effective way to treat BTC. The expression profiles of IL-21 and IL-33 hold promise as potential markers for guiding the chemotherapy combined with immunotherapy in BTC patients.