Microwave versus cryoablation and radiofrequency ablation for small renal mass: a multicenter comparative analysis

Background: Ablative techniques emerged as effective alternative to nephron-sparing surgery for treatment of small renal masses. Radiofrequency ablation (RFA) and cryoablation (CRYO) are the two guidelines-recommended techniques. Microwave ablation (MWA) represents a newer technology, less described. The aim of the study was to compare outcomes of MWA to those of CRYO and RFA. Methods: Retrospective investigation of patients who underwent MWA, CRYO, or RFA from seven high-volume US and European centers was performed. The first group included patients who underwent CRYO or RFA; the second MWA. We collected baseline characteristics, clinical, intraoperative, and postoperative data. Oncological data included technical success, local recurrence, and progression to metastasis. Multivariate analysis was performed to find predictors for postoperative complications. A composite outcome of "trifecta" was used to assess surgical, functional, and oncological outcomes. Results: 739 patients underwent CRYO or RFA and 50 MWA. CRYO/RFA group had significantly longer operative time (P<0.001), but no difference in LOS, postprocedural Hb mean, intraprocedural complications (P=0.180), overall postprocedural complication rates (P=0.126), and in the 30-day re-admission rate (P=0.853) were detected. No predictive parameter of postprocedural complications was found. Concerning functional outcome, no differences were detected in terms of eGFR at 1 year (P=0.182), ΔeGFR at 1 year (P=0.825) and eGFR at latest follow-up (P=0.070). "Technical success" was achieved in 98.6% of the cases (MWA=100%, CRYO/RFA=98.5%; P=0.775), and there was no significant difference in terms of 2-year recurrence rate (P=0.114) and metastatic progression (P=0.203). Trifecta was achieved in 73.0% of CRYO/RFA vs. 69.6% of MWA cases (P=0.719). Conclusions: MWA is a safe and effective treatment option for small renal masses. Compared with CRYO/RFA, it seems to offer low complication rates, shorter operation time, and equivalent surgical and functional outcomes.