CT-based renal artery caliber change as a potential imaging marker of treatment response in renal cell carcinoma; an exploratory imaging study

To evaluate whether treatment-induced changes in tumor-bearing renal artery caliber on contrast-enhanced CT are associated with pathological response and pathological downstaging after systemic therapy in locally advanced or metastatic renal cell carcinoma (RCC), and to explore the clinical relevance of this vascular parameter. We retrospectively analyzed 43 patients with locally advanced or metastatic RCC who underwent systemic therapy followed by nephrectomy. Renal artery inner diameter was measured on arterial-phase CT before and after treatment using curved planar reformation. Interobserver reproducibility of the measurement was excellent (intraclass correlation coefficient ICC = 0.992). A subset of 33 patients had adequate bilateral imaging for tumor-bearing versus contralateral comparison. Tumor size was measured as the longest axial diameter on contrast-enhanced CT, and tumor shrinkage was expressed as percentage change from baseline according to RECIST 1.1 measurement principles. Choi criteria incorporated tumor size and attenuation changes. Pathological response was defined as the proportion of treatment-induced necrosis and fibrosis. Associations between arterial caliber change, pathological response, and pathological downstaging were assessed. Multivariable regression analysis identified independent predictors of pathological response. Discriminative ability for downstaging was evaluated using receiver operating characteristic analysis. At baseline, the tumor-bearing renal artery had a larger inner diameter than the contralateral artery. After systemic therapy, its diameter significantly decreased (6.35 to 5.65 mm, p < 0.001). In the paired subset (n = 33), significant reduction occurred only in tumor-bearing arteries. Percentage diameter reduction correlated with pathological response (r = 0.314, p = 0.040). Patients with pathological downstaging showed greater diameter reduction than those without downstaging (16.3% vs 6.83%, p = 0.021). Tumor size change based on RECIST principles and Choi criteria were not significantly associated with downstaging. Multivariable analysis confirmed renal artery diameter change rate as an independent predictor of pathological response. ROC analysis showed moderate discrimination for downstaging (AUC 0.71, 95% CI: 0.55–0.87). Reduction in tumor-bearing renal artery caliber was independently associated with pathological response and downstaging. This vascular parameter may complement conventional tumor-centered imaging criteria in selected patients. Not applicable