Outcomes of Microwave Ablation for Small Renal Masses: A Single Center Experience.

To investigate the safety of microwave ablation (MWA) as an emerging technology for treating small renal masses.

Patients with renal masses treated at a high-volume center with MWA between March 2015 and June 2019 were retrospectively identified. Safety, changes in renal function, primary treatment efficacy, and the natural history of imaging characteristics of masses post-ablation were examined.

Forty-five patients underwent MWA during the study period. Median age was 71 years (range 31-87). Median RENAL nephrometry score was 6 (range 4-9) with mean tumor size 2.6±0.7 cm. Thirty-three percent of tumors were within 4 mm of the collecting system. Median total microwave energy applied was 400 Watts (range 105-2600 Watts). There was no significant change in creatinine (p=0.21) or GFR (p=0.09) from pre-operative to post-operative day one (POD#1) levels. There was a statistically but not clinically significant decrease in hemoglobin from pre-operative to POD#1 levels (estimated -0.06 from seven days before procedure to POD#1, p=0.02). There was no durable change in creatinine (p=0.16) or GFR (p=0.72) at median follow up of 7.5 months. There were four (9%) complications: three Clavien grade 1 and one Clavien grade 3 that led to loss of the kidney. Tumor size decreased postoperatively by an estimated -0.03 cm/month (range 0-1.9 cm, p<0.01). Initial technical success was 100%. Primary treatment efficacy was 94%.

MWA shows promise as an alternative thermal ablative technique with excellent short-term outcomes.

Journal of endourology. 2020 Jul 01 [Epub ahead of print]

Courtney Yong, Sarah L Mott, Sandeep Laroia, Chad Robert Tracy

University of Iowa, Urology, 200 Hawkins Drive, Iowa City, Iowa, United States, 52241; ., University of Iowa, Holden Comprehensive Cancer Center, Iowa City, Iowa, United States; ., University of Iowa, Interventional Radiology, Iowa City, Iowa, United States; ., University of Iowa, Urology, 200 Hawkins Dr., 3 RCP, Iowa City, Iowa, United States, 52242-1089; .