Prognostic role of systemic immune-inflammation index in solid tumors: a systematic review and meta-analysis

Background: Inflammation may play an important role in cancer progression, and a higher systemic immune-inflammation index (SII) has been reported to be a poor prognostic marker in several malignancies. However, the results of published studies are inconsistent. Materials and Methods: A systematic review of databases was conducted to search for publications regarding the association between blood SII and clinical outcome in solid tumors with a date up to February 12, 2017. The primary outcome was overall survival (OS) and the secondary outcomes were progression-free survival (PFS) and cancer-specific survival (CSS). Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were used to assess the strength of the association between blood SII and clinical outcome in solid tumors. Results: A total of 15 articles were included in the analysis. Overall, systemic immune-inflammation index greater than the cutoff predicted poor overall survival (HR = 1.55, 95% CI = 1.27-1.88; P < 0.001). Subgroup analyses revealed that high systemic immune-inflammation index indicated a worse overall survival in hepatocellular carcinoma (P < 0.001), urinary cancers (P < 0.001), gastrointestinal tract cancers (P = 0.02), small cell lung cancer (P < 0.05) and acral melanoma (P < 0.001). Hazard ratio for systemic immune-inflammation index greater than the cutoff for cancer-specific survival was 1.44 (P < 0.05). Conclusions: Elevated systemic immune-inflammation index is associated with a worse overall survival in many solid tumors. The systemic-inflammation index can act as a powerful prognostic indicator of poor outcome in patients with solid tumors.