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

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).

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).

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).

Microwave ablation provides higher TRIFECTA achievement, and shorter OT than RFA. No significant differences were found regarding the LRR.