Thermal ablation of the small renal mass: Case selection using the R.E.N.A.L.-nephrometry Score

Objectives: Treatment decision-making for localized renal lesions remains overly subjective. While the AUA Guidelines list thermal ablation (TA) as a treatment option for the clinical T1 renal mass, few data exist regarding the relationship between TA and tumor complexity. The R.E.N.A.L.-Nephrometry Scoring System (NS) was introduced to objectify salient renal mass anatomy and standardize academic reporting. Here we correlate the salient anatomical attributes of renal masses undergoing TA with technical and oncologic outcomes. Materials and methods: We queried our prospectively maintained kidney cancer database of 2,312 patients and identified 39 patients who underwent TA with available nephrometry scores. Patient clinical, technical, functional, and oncologic characteristics were reviewed. Results: Median patient age, serum creatinine, estimated glomerular filtration rate, and Charlson Comorbidity Index were 71 (range = 57-86) years, 1.37 (range = 0.7-3.5) mg/dl, 57.1 (range = 23.3-93.8) ml/min, and 2 (range = 0-5), respectively. Median Nephrometry Score for patients undergoing tumor ablation was 6 (4-10). Low (NS = 4-6), moderate (NS = 7-9), and high (NS = 10-12) complexity tumors were identified in 20 (51.3%), 17 (43.6%), and 2 (5.1%) patients. Six (15%) patients experienced a tumor recurrence. Of those with a recurrence, 5/6 (83.3%) had moderate complexity tumors with the remaining tumor being low complexity. Minor and major Clavien complications occurred in 4 (10%) and 1 (3%) patients, all of whom had moderate complexity tumors. Conclusions: At our institution, 95% of tumors undergoing TA were anatomically low or moderate complexity lesions as measured by the R.E.N.A.L.-Nephrometry Scoring System. Nephrometry may help predict disease recurrence and peri-procedural complications, yet multi-institutional analysis is needed to further validate these findings.