Abstract No. 225 External Validation of the Ability of the mRENAL Nephrometry Score to Identify Patients at Risk for Major Adverse Events or Local Tumor Recurrence After Percutaneous Renal Cryoablation

The modified RENAL (mRENAL) nephrometry score previously outperformed the RENAL nephrometry score in identifying patients at risk for major adverse events (AEs) from percutaneous renal cryoablation (PCA) at a single institution, using their local patient population. However, the mRENAL score has never been validated against an external patient population. The purpose of this study was to evaluate the ability of the mRENAL score to identify patients at risk of either major AEs and/or local tumor recurrence (LR) after PCA in an external patient population. Institutional review board–approved, HIPAA-compliant retrospective review of consecutive adult patients with renal tumors treated with PCA. Patients with benign histology and patients treated with radiofrequency ablation, microwave ablation, or irreversible electroporation were excluded. Patient demographic data were recorded. The RENAL and mRENAL nephrometry scores were calculated. Clinical outcomes such as AEs, LR, cancer-specific survival (CSS), and overall survival (OS) were collected. AEs were classified according to Society of Interventional Radiology criteria. Continuous variables and categorical variables were analyzed using the Wilcoxon rank sum test and chi-square test, respectively. Logistic regression analysis was performed to identify variables associated with major AEs or LR. 207 patients (males: n=117 (56.5%)) with a mean age of 65.8 (STD:11.2) years (range:27-90) were included. Overall, the mean tumor diameter, RENAL score, and mean mRENAL score were 30.1 mm (STD:11.4), 6.3 (STD:1.7), and 6.8 (STD:1.9), respectively. 14 patients (6.8%) and 13 patients (6.3%) experienced a major AE or LR after PCA, respectively. CSS and OS were 98.6% and 90.3%, respectively. For patients with major AEs after PCA, the mean tumor diameter (p< 0.0001), mean RENAL score (p=0.03), and mean mRENAL score (p=0.009) were all higher than those for patients without a major AE. Multi-variate regression analysis showed that only mean tumor diameter (p=0.005) was predictive of a major AE. There were no statistically significant differences between patients with LR and patients without LR after PCA with regards to tumor size (p=0.07), mean RENAL score (p=0.32), or mean mRENAL score (p=0.07). Multi-variate regression analysis showed that only mean tumor diameter (p=0.01) was predictive of LR. The mRENAL score did not accurately identify patients at risk for either major AEs or LR after PCA. Maximum tumor diameter alone was predictive of both major AEs and LR, and should be the primary focus during patient selection.