Peri-operative and local control outcomes of robot-assisted partial nephrectomy vs percutaneous cryoablation for renal masses: comparison after matching on radiological stage and renal score

Objectives: To compare the oncological outcomes of percutaneous cryoablation (PCA) vs robot-assisted partial nephrectomy (RAPN) for the treatment of T1 renal tumours.

Patients and methods: We conducted a retrospective study in all patients treated by RAPN or PCA for malignant renal tumours in one of four centres between 2009 and 2016. Tumours were paired one by one using radiological tumour stage and RENAL nephrometry score (package matchit, R software version 3.2.2). Malignancy was confirmed by biopsy for all patients in the PCA group. Patient characteristics before and after matching and oncological results were compared between the two groups. Cox regression, adjusted for age, treatment type, histological type and margins, was used to identify factors associated with time to local recurrence. Positive margins were defined histologically in the RAPN group and radiologically in the PCA group.

Results: A total of 647 patients were identified; 470 underwent RAPN and 177 underwent PCA. After matching, there was no significant difference between the two groups (RAPN, n = 177; PCA, n = 177) with regard to tumour stage, RENAL nephrometry score, tumour size (27.6 vs 25.9 mm; P = 0.07) and gender ratio. Patients in the PCA group remained significantly older (69.9 vs 59.8 years; P < 0.001). The absolute recurrence rate was 2.8% in the RAPN group vs 8.4% in the PCA group (P = 0.03). The 5-year recurrence-free survival rate was 85% in the PCA group vs 95% in the RAPN group (log-rank P = 0.02). In multivariate analysis, the presence of positive margins and the type of treatment were the two factors significantly associated with local recurrence (P < 0.001 and P = 0.046, respectively).

Conclusion: The local recurrence rate after PCA was significantly higher than after RAPN for T1 renal tumours. Incomplete treatment was the main criterion associated with recurrence. The recurrence rate may have been overestimated in the PCA group because of closer radiological follow-up in these patients.