Percutaneous microwave ablation of renal masses in a UK cohort

Objectives To report a tertiary referral centre's experience of microwave ablation (MWA) for suspected renal cell carcinoma (RCC), describing complications and oncological outcomes. Patients and Methods Consecutive MWA procedures (n = 113) for renal masses (October 2016 to September 2019) were maintained on a prospective database. Data describing patient, disease, procedure, complications, and oncological outcomes were analysed. Results The median (range) age was 68 (33-85) years, 73% were male, and the median Charlson Comorbidity Index was 0. The median (interquartile range [IQR]) tumour diameter was 25 (20-32) mm. In all, 95% had renal mass biopsy, with histologically confirmed cancer in 75%. The median (IQR) R.E.N.A.L. (Radius, Exophytic/Endophytic, Nearness, Anterior/Posterior, Location) nephrometry score was 7 (6-8). The median ablation time was 6 min and length of stay was 1 day for 95% of the patients. Clavien-Dindo complication Grades I, II, IIIb and IV occurred in 18%, 1.8%, 0.9% and 0.9%, respectively. The median follow-up was 12 months and the median (IQR) renal function change was -4 (-18 to 0)%. One patient (0.9%) had local recurrence, treated with re-ablation; two developed metastatic progression; and two (1.8%) had indeterminate findings on follow-up (one lung nodule and one possible local recurrence), managed with ongoing protocolised computed tomography surveillance. Post-procedure complications were associated with total ablation time (odds ratio [OR] 1.152/min, 95% confidence interval [CI] 1.040-1.277) and total ablation energy (OR 1.017/kJ, 95% CI 1.001-1.033). Conclusions We describe the largest UK series of MWA treatment for T1a/small T1b renal masses to date. MWA was well tolerated, with 95% discharged the following day and low complication/re-admission rates. Current follow-up demonstrates favourable disease control. MWA appears to be safe and effective and should be considered in future prospective comparisons of treatments for T1a/small T1b renal masses.