Systemic Immune–Inflammation Index Predicts Prognosis of Cancer Immunotherapy: Systemic Review and Meta-Analysis

Objective: This meta-analysis was designed to explore the association between the systemic immune–inflammation index (SII) and the therapeutic effect of immune checkpoint inhibitors. Materials & methods: The authors retrieved relevant studies published before May 25, 2022. Hazard ratio (HR) with 95% CI was used to evaluate the relationship between SII and overall survival (OS) and progression-free survival (PFS). Results: 14 articles comprising 2721 patients were included in this study. The pooled results proved that high SII levels were closely related to poor prognosis in cancer patients receiving immune checkpoint inhibitors (OS HR = 2.40; 95% CI: 2.04–2.82; PFS HR = 1.57; 95% CI: 1.33–1.86) and that an SII value of 750 was appropriate as a cut-off value (OS HR = 2.20; 95% CI: 1.83–2.63; PFS HR = 1.54; 95% CI: 1.33–1.80). Conclusion: High SII levels (>750) may be an indicator of worse OS and PFS in cancer patients treated with immune checkpoint inhibitors.