Abstract
Our study aimed to examine the predictive relevance of the Systemic Immune-Inflammation Index (SII) in patients with metastatic castration-resistant prostate cancer (mCRPC). A total of 113 mCRPC patients were assessed. In this descriptive study, SII was calculated using the formula (neutrophil count × platelet count)/lymphocyte count. The optimal threshold for SII, determined via the ROC curve, was 700. Patients with SII ≤ 700 were classified as SII-low, while those with SII > 700 were categorized as SII-high. The median overall survival (mOS) was significantly longer in the low SII group compared to the high SII group (*P = 0.015). In multivariate analysis, Gleason score, albumin levels, CHAARTED volume, and SII were identified as significant prognostic factors. Our findings indicate that SII has a strong correlation with survival and can serve as an independent prognostic marker in mCRPC patients.