Percutaneous Microwave Ablation of Small (<4 cm) Renal Masses Performed under Moderate Sedation

To determine the technical success, adverse events, local tumor recurrence, and survival in adult patients undergoing microwave ablation (MWA) of small renal masses performed exclusively under moderate sedation.

A single-institution, retrospective review from 2016 to 2023 of percutaneous, computed tomography-guided MWA for small renal masses (<4 cm) was performed. After addressing exclusion criteria, 66 patients undergoing 72 ablations were included. Patient demographics, comorbidities, tumor characteristics, procedural details, and clinical outcomes were evaluated. Kaplan-Meier analysis of progression-free survival (PFS), cancer-specific survival (CSS), and overall survival (OS) was performed. Kidney function before and after ablation was compared using the nonparametric Mann-Whitney U test.

Seventy-two small renal masses with a mean size of 2.2 cm (SD ± 0.7) underwent MWA with a 2.45-GHz gas-cooled MWA system at 65 W for 5-15 minutes (mean, 39.1 kJ) performed under moderate sedation. Demographics included a mean age of 68.4 years (SD ± 8.3) (n = 62 men) and Charlson Comorbidity Index score of 6.2 (SD ± 2.1). Median sedation doses were 150 mcg (interquartile range [IQR], 100-175 mcg) of fentanyl and 2.5 mg (IQR, 2-3.5 mg) of midazolam. Technical success was 100%, and all patients were discharged the same day. Median follow-up duration was 3.1 years. PFS and OS were 88.1% and 91.9% at 3 years, respectively. CSS was 100%. There were 2 mild adverse events (2.8%) and 3 recurrences (4.2%). Only 9.7% (n = 5) of patients required postprocedural analgesia; no patients required postdischarge analgesic prescriptions.

MWA of small renal masses under moderate sedation alone demonstrates excellent patient safety profile, tolerability, and effectiveness, allowing operational efficiency, including short procedure times and same-day discharge.