Systemic immune-inflammation index is a stage-dependent prognostic factor in patients with operable non-small cell...

Immune function is a key component affecting tumor progression in patients with cancer. The purpose of this study was to identify the prognostic value of systemic immune-inflammation index (SII) in patients with non-small cell lung cancer (NSCLC) and the differences of its prognostic value in patients with distinct characteristics.

Patients with completely resected NSCLC were reviewed according to the eighth TNM classification of lung cancer. Patients were further categorized into the low- and high-SII groups. Cox proportional hazard analyses were performed to identify the independent prognostic factors.

A total of 3984 patients with NSCLC were enrolled in this study. Kaplan-Meier analyses demonstrated that high SII was associated with worse recurrence-free survival (RFS) (P<0.001) and overall survival (OS) (P<0.001). Cox proportional hazard analyses revealed that SII was an independent risk factor for worse RFS (P=0.038) and OS (P=0.043). Further analyses demonstrated that the prognostic value of SII was observed only in patients with stage I disease (P<0.001), solid nodules (P=0.002), or adenocarcinoma (P<0.001). Sensitivity analyses using multiple imputation and competing risk analyses also confirmed similar results.

SII was associated with worse survival independently, and its prognostic role was exhibited solely in NSCLC patients with stage I disease, solid nodules, and adenocarcinoma. This study helped us specify the target population for clinical use of SII.