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

Abstract

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.

Keywords: meta-analysis; solid tumors; systemic immune-inflammation index.

Figure 1. Flow diagram of included studies for this meta-analysis

Figure 2. Forest plots of studies evaluating the association between SII and overall survival

The center of each square represents the HR, the area of the square is the number of sample and thus the weight used in the meta-analysis, and the horizontal line indicates the 95% CI.

Figure 3. Univariate meta-regression exploring the association of the cutoff used to define SII and the hazard ratio for overall survival

Figure 4. Funnel plots of hazard ratio for overall survival for high SII (horizontal axis) and the standard error (SE) for the hazard ratio (vertical axis)

Each study is represented by one circle. The vertical line represents the pooled effect estimate.