Systemic Immune-Inflammation Index as a Predictor of Progression in Melanoma: A Retrospective Cohort Study

Systemic inflammation plays a pivotal role in melanoma progression through mechanisms of immune suppression, angiogenesis, and metastatic dissemination. The systemic immune-inflammation index (SII), integrating platelet, neutrophil, and lymphocyte counts, has emerged as a composite biomarker reflecting the balance between tumor-promoting inflammation and host immune response.

This study aimed to evaluate the prognostic value of the SII in predicting 12-month progression-free survival (PFS) in patients with melanoma and to determine whether elevated SII independently correlates with disease progression after adjustment for clinical stage and age.

A retrospective cohort study was conducted, including 40 patients with histopathologically confirmed melanoma between 2019 and 2024. Baseline SII was calculated as (platelet count × neutrophil count) / lymphocyte count, using a validated cutoff of 560. Statistical analyses were performed using Jamovi version 2.4. Associations between SII and 12-month outcomes were assessed using chi-square and logistic regression analyses, while Kaplan-Meier and ROC analyses evaluated prognostic performance.

An SII ≥560 was significantly associated with higher progression risk (relative risk (RR) 5.3; odds ratio (OR) 22.7, 95% confidence interval (CI) 4.4-117.5; p < 0.001). Patients with elevated SII had markedly reduced 12-month PFS (20% vs. 85%; log-rank = 16.5, p < 0.001). SII showed excellent discriminative ability (area under the curve (AUC) 0.91, 95% CI 0.83-0.99). In multivariable analysis, SII remained independently predictive of progression (adjusted OR 14.6; 95% CI 2.3-91.8; p = 0.004).

The SII independently predicted 12-month disease progression in melanoma, identifying high-risk patients even within early stages. These findings support its role as a simple, reproducible, and low-cost biomarker for preoperative risk assessment and individualized follow-up. Future prospective multicenter studies with larger cohorts and extended follow-up are warranted to validate these results and to better define the clinical utility of SII as part of comprehensive melanoma risk stratification strategies.