Immune-inflammation index as prognostic markers in metastatic castration-resistant prostate cancer: a systematic review and meta-analysis

Introduction Systemic inflammation is closely linked to tumor progression and immune dysfunction. Simple blood-derived immune-inflammatory indices may provide cost-effective prognostic stratification for metastatic castration-resistant prostate cancer. Methods This systematic review and meta-analysis followed PRISMA 2020 and was registered in PROSPERO. Electronic databases, including Embase, PubMed, Web of Science, and the Cochrane Library, were queried from inception until May 2025. Eligibility was restricted to research comparing high and low strata of the systemic immune-inflammation index (SII), lymphocyte-to-monocyte ratio (LMR), and ratios of neutrophils or platelets to lymphocytes, provided they reported survival outcomes (OS and/or PFS) via hazard ratios (HRs) and 95% confidence intervals (CIs). Random-effects models were applied according to heterogeneity; subgroup, sensitivity, and publication-bias analyses were performed. Results 36 studies involving 10,325 patients with mCRPC were included. Elevated NLR was associated with worse OS (pooled HR = 1.77, 95% CI 1.59–1.97) and PFS (pooled HR = 1.51, 95% CI 1.31–1.75). Higher PLR predicted shorter OS (pooled HR = 1.57, 95% CI 1.35–1.84) and PFS (pooled HR = 1.45, 95% CI 1.13–1.87). Higher LMR was associated with improved OS (pooled HR = 0.45, 95% CI 0.31–0.67), while higher SII predicted worse OS (pooled HR = 2.22, 95% CI 1.86–2.66). Subgroup analyses (where feasible) supported the robustness of NLR/PLR associations across several clinical strata, though some subgroups were limited by small numbers. Conclusion Blood-based immune-inflammatory indices (NLR, PLR, SII, LMR) are significantly associated with survival outcomes in mCRPC. These readily available markers may aid risk stratification and inform individualized management, while prospective validation and standardized cut-offs remain needed. Systematic Review Registration https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=1291003 , identifier CRD420261291003.