Pretreatment systemic immune-inflammation index and prognostic nutritional index in advanced or metastatic non-small cell lung cancer: a systematic review and meta-analysis

The systemic immune-inflammation index (SII) and prognostic nutritional index (PNI) have been proposed as prognostic biomarkers in solid tumors, but their value in advanced or metastatic non-small cell lung cancer (NSCLC) remains uncertain. This systematic review and meta-analysis evaluated the prognostic significance of pretreatment SII and PNI for overall survival (OS) and progression-free survival (PFS) in this population. We systematically searched major databases for studies reporting the association between pretreatment SII or PNI and survival outcomes in advanced or metastatic NSCLC. Hazard ratios (HRs) were pooled using meta-analytic methods, and heterogeneity across studies was assessed. Elevated pretreatment SII was associated with poorer survival outcomes in advanced or metastatic NSCLC, while reduced PNI also tended to indicate unfavorable prognosis. However, the magnitude and direction of the associations varied across studies, and substantial heterogeneity was observed, suggesting that treatment context, cutoff selection, and patient characteristics may influence prognostic effects. Pretreatment SII and PNI are promising prognostic biomarkers in advanced or metastatic NSCLC. Elevated SII and reduced PNI may identify patients at higher risk of poor outcomes, but further prospective studies using standardized biomarker cutoffs and rigorous prognostic methodology are needed to validate these findings.