Preoperative Systemic Immune-Inflammation Index Combined With Multiphasic Enhanced CT Features for Predicting Fuhrman Grade in Clear Cell Renal Cell Carcinoma: An Internally Validated Proof-of-Concept Nomogram.

BACKGROUND: Accurate preoperative estimation of tumour grade may guide management decisions for clear cell renal cell carcinoma (ccRCC); however, grade is typically confirmed only postoperatively. This study evaluated whether an internally validated proof-of-concept model combining the systemic immune-inflammation index (SII) with multiphasic computed tomography (CT) features could identify high Fuhrman grade preoperatively, while acknowledging that this endpoint is not interchangeable with World Health Organization/International Society of Urological Pathology (WHO/ISUP) grade without revalidation. METHODS: This study retrospectively analysed 286 surgically treated patients with pathologically proven ccRCC between January 2018 and December 2023. Patients were randomly assigned to training (n = 200) and internal validation (n = 86) cohorts. SII was calculated from preoperative platelet, neutrophil, and lymphocyte counts and modelled continuously; the SII cutoff of 530 was used only for sensitivity analysis and nomogram display. Variables with p < 0.10 in univariable logistic regression and variables considered clinically important were entered into multivariable logistic regression with backward stepwise selection. Collinearity diagnostics, area under the curve (AUC) comparison, calibration, decision curve analysis, bootstrap resampling, and risk stratification were performed. RESULTS: High-grade ccRCC (Fuhrman III/IV) accounted for 31.1% of cases. In multivariable analysis, continuous SII (odds ratio (OR) = 1.39 per 100-unit increase, 95% confidence interval (CI): 1.18-1.63, p < 0.001), tumour size >4 cm (OR = 3.06, 95% CI: 1.44-6.52, p = 0.004), intratumoral necrosis (OR = 4.71, 95% CI: 2.26-9.83, p < 0.001), and corticomedullary phase (CMP) enhancement ≤84 Hounsfield unit (HU; OR = 2.11, 95% CI: 1.10-4.04, p = 0.024) were independently associated with high-grade disease. The nomogram achieved AUCs of 0.891 (95% CI: 0.846-0.936) and 0.867 (95% CI: 0.793-0.941) in the training and validation cohorts. Adding SII to CT features improved the validation AUC by 0.036 and improved reclassification metrics. CONCLUSIONS: This internally validated proof-of-concept nomogram integrates continuous SII and routine enhanced CT features to estimate the probability of high Fuhrman grade in surgically treated ccRCC. It may facilitate preoperative discussions in similar clinical settings, but external validation using centralized WHO/ISUP grading is required before broad implementation.