Utility of Systemic Immune-Inflammation Index and Karnofsky Performance Status in Evaluating Short-Term Clinical Outcomes after Whole-Brain Radiotherapy in Patients with Brain Metastases from Solid Tumors

Abstract

Background: Brain metastases are the most common brain tumors in adults with solid cancers and are associated with poor outcomes. Whole brain radiotherapy (WBRT) is the standard treatment for patients with multiple brain lesions, but responses vary. Prognostic markers are essential to guide treatment decisions. This study specifically evaluated the utility of the Systemic Immune-inflammation Index (SII) and Karnofsky Performance Status (KPS) in predicting clinical outcomes after WBRT. The study introduces a novel approach by analyzing SII without using a predetermined cut-off, instead stratifying patients using the median SII value, which is more applicable in a cohort where all patients already have advanced metastatic disease. Methods: A retrospective cohort study was conducted on 33 patients with brain metastases from solid tumors who underwent WBRT at Dr. Hasan Sadikin General Hospital between January 2019 and January 2024. Data collected included demographics, primary tumor type, neurological symptoms, baseline SII, and baseline KPS. Mortality and functional status were assessed two months after WBRT. Comparisons between groups were performed using the independent t-test or Mann-Whitney U test for continuous variables, and the Chi-square or Fisher’s Exact test for categorical variables. Changes in KPS before and after WBRT were analyzed using the Wilcoxon signed-rank test. Results: Patients who died had significantly higher SII and lower baseline KPS (p < 0.001). Seizures and altered consciousness were strongly associated with 2-month mortality (p < 0.001), whereas headache was associated with lower KPS post-WBRT (p < 0.001). Functional status (KPS) significantly improved two months after WBRT (p = 0.030). Baseline demographic factors were not significantly associated with outcomes. Because all patients had advanced metastatic disease, no universal SII cut-off was clinically appropriate; instead, the median SII across the cohort provided a more meaningful way to distinguish high versus low inflammatory status. Conclusion: SII and KPS demonstrated strong prognostic value in predicting survival and functional outcomes after WBRT. The use of median-based SII categorization represents a practical and novel approach for real-world settings where a validated cut-off may not apply. Early identification of elevated SII and low KPS may help clinicians personalize treatment strategies for patients with brain metastases.