Comprehensive assessment of renal tumour complexity in a large percutaneous cryoablation cohort

OBJECTIVE: To evaluate the association between renal tumour complexity and outcomes in a large cohort of patients undergoing percutaneous cryoablation (PCA). PATIENTS AND METHODS: Patients with renal tumours treated with PCA were identified using our prospectively maintained ablation registry (2003-2015). Salvage procedures and inherited tumour syndromes were excluded. The associations between R.E.N.A.L. nephrometry score (NS) and risk of complications, renal function impairment, local failure and cancer-specific mortality (CSM) were evaluated using univariate and multivariable logistic, linear and Cox regression models. RESULTS: The cohort included 618 tumours treated during 580 procedures in 565 patients. The median (interquartile range [IQR]) follow-up was 34 (14.66) months. Complications (any grade) during a procedure (n[total] = 87, 15%) were more frequent with higher NS (NS 4-6: 10%; NS 7-9: 14%; NS 10-12: 36%; P < 0.001). Higher NS was independently associated with risk of complications (odds ratio [OR; per 1 point] = 1.3; 95% confidence interval [CI] 1.2-1.5; P < 0.001). Of all the NS components, tumour size was the most strongly associated with complication risk (OR 3.4; 95% CI 2.2-5.2; P < 0.001). The median (IQR) decline in glomerular filtration rate (GFR) from baseline was 9% (0, 22) at last follow-up. Each additional point in NS was associated with a 1.3% (95% CI 0.4-2.1; P = 0.005) greater GFR decline from baseline. NS was not significantly associated with local failure (n [total] = 14, 2%; NS 4-6: 2%; NS 7-9: 3%; NS 10-12: 5%; P = 0.32) or CSM (n [total] = 8, 2%; NS 4-6: 2%; NS 7-9: 3%; NS 10-12: 2%; P = 0.88). CONCLUSION: In high-complexity tumours PCA was associated with a tumour size-driven increased risk of post-procedural complications. Higher NS was associated with a small, clinically minor additional decline in renal function. Risks for local failure and CSM were low, regardless of tumour complexity.