Microwave vs radiofrequency ablation for small renal masses: perioperative and oncological outcomes

Objective: To conduct a comprehensive comparison of microwave ablation (MWA) vs radiofrequency ablation (RFA) outcomes in the treatment of small renal masses (SRMs), specifically: TRIFECTA ([i] complete ablation, [ii] absence of Clavien–Dindo Grade ≥III complications, and [iii] absence of ≥30% decrease in estimated glomerular filtration rate) achievement, operative time (OT), and local recurrence rate (LRR). Patients and Methods: We retrospectively analysed 531 patients with SRMs (clinical T1a–b) treated with MWA or RFA at a single centre (2008–2022). First, multivariable logistic regression models were used for testing TRIFECTA achievement. Second, multivariable Poisson regression models were used to evaluate variables associated with longer OT. Finally, Kaplan–Meier plots depicted LRR over time. All analyses were repeated after 1:1 propensity score matching (PSM). Results: Of 531 patients with SRMs, 373/531 (70.2%) underwent MWA and 158/531 (29.8%) RFA. MWA demonstrated superior TRIFECTA achievement (314/373 [84.2%]) compared to RFA (114/158 [72.2%], P = 0.001). These differences were driven by higher rates of complete ablation in MWA- vs RFA-treated patients (348/373 [93.3%] vs 137/158 [86.7%], P < 0.001). In multivariable logistic regression models, MWA was associated with higher TRIFECTA achievement, compared to RFA, before (odds ratio [OR] 1.92, P = 0.008) and after PSM (OR 1.99, P = 0.023). Finally, the median OT was shorter for MWA vs RFA (105 vs 115 min; P = 0.002). At Poisson regression analyses, MWA predicted shorter OT before (incidence rate ratio [IRR] 0.86, P < 0.001) and after PSM (IRR 0.85, P < 0.001). Local recurrence occurred in 17/373 (4.6%) MWA-treated patients and 21/158 (13.3%) RFA-treated patients (P = 0.29) after a median (interquartile range) follow-up of 24 (8–46) months. There were no differences in the LRR in Kaplan–Meier plots before (P = 0.29) and after PSM (P = 0.42). Conclusion: Microwave ablation provides higher TRIFECTA achievement, and shorter OT than RFA. No significant differences were found regarding the LRR.