Systemic Immune-Inflammation Index in Cancer Prognosis
Summary
The Systemic Immune-Inflammation Index (SII) is a composite biomarker derived from peripheral neutrophil, lymphocyte and platelet counts. By integrating markers of inflammation and immune competence, SII reflects the dynamic interplay between tumour-promoting inflammation and host antitumour response. Elevations in neutrophils and platelets contribute to tumour progression through angiogenesis, extracellular matrix remodelling and suppression of cytotoxic lymphocytes, whereas lymphocytes mediate immune surveillance. Across a broad spectrum of malignancies, a high SII has been consistently linked to poorer overall survival, disease-free survival and progression-free survival. Its ease of measurement, low cost and reproducibility make it highly attractive for risk stratification, therapeutic decision-making and monitoring response to surgery, targeted therapies and immunotherapy, particularly in resource-constrained settings.
Research from Nature Portfolio
In HER2-positive breast cancer, pretreatment SII has been shown to distinguish patients likely to derive long-term benefit from trastuzumab therapy. Patients with lower SII experienced significantly higher five-year disease-free survival following adjuvant trastuzumab, whereas those with elevated SII had markedly shorter intervals to recurrence, highlighting SII’s potential to refine patient selection for targeted therapy.
In cervical cancer, an updated investigation demonstrated that a high preoperative SII independently predicts poorer overall survival and disease-free survival after radical resection. SII outperformed other systemic indices and retained prognostic value across all FIGO stages. Incorporation of SII into a nomogram enhanced the accuracy of postoperative survival predictions, underscoring its clinical utility.
Foundational work in oesophageal squamous cell carcinoma revealed SII as an independent risk factor for overall survival, outperforming neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios. Propensity-matched analysis confirmed its robustness, establishing SII as a simple yet powerful predictor in patients undergoing curative esophagectomy.
Systemic Immune-Inflammation Index in Cancer Prognosis publication trend
The graph below shows the total number of articles in systemic immune-inflammation index in cancer prognosis across all publications each year (not limited to Nature Index journals).
Technical terms
Systemic Immune-Inflammation Index (SII): A prognostic score calculated as platelet count × neutrophil count/lymphocyte count.
Hazard Ratio (HR): A measure of the relative risk of an event (e.g. death or progression) occurring in one group compared to another over time.
Overall Survival (OS): The interval from diagnosis or treatment initiation to death from any cause.
Progression-Free Survival (PFS): The length of time during and after treatment that a patient lives without disease progression.
Immune Checkpoint Inhibitor (ICI): A class of therapies that block proteins such as PD-1 or CTLA-4 to enhance antitumour immune responses.
References
- Preoperative systemic immune-inflammation index as a prognostic indicator for patients with urothelial carcinoma. Frontiers in Immunology (2023).
- Inflammation and Colorectal Cancer: A Meta-Analysis of the Prognostic Significance of the Systemic Immune–Inflammation Index (SII) and the Systemic Inflammation Response Index (SIRI). International Journal of Molecular Sciences (2024).
- Prognostic and clinicopathological significance of Systemic Immune-Inflammation Index in cancer patients receiving immune checkpoint inhibitors: a meta-analysis. Annals of Medicine (2023).
- Systemic immune-inflammation index as a prognostic marker in HER2-positive breast cancer patients undergoing trastuzumab therapy. Scientific Reports (2024).
- Prognostic Value of Preoperative Systemic Immune-Inflammation Index in Patients with Cervical Cancer. Scientific Reports (2019).
- Systemic Immune-Inflammation Index Predicts Prognosis of Patients with Esophageal Squamous Cell Carcinoma: A Propensity Score-matched Analysis. Scientific Reports (2016).
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