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

To evaluate the association between renal tumour complexity and outcomes in a large cohort of patients undergoing percutaneous cryoablation (PCA).

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.

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).

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.