CIO 2022-21 Outcome of Microwave Ablation of Stage 1a Renal Cell Carcinoma in a Community-Based Practice

Purpose: Thermal ablation is recommended as an option for category T1a renal cell carcinoma (RCC) when there are major comorbidities and an increased surgical risk for invasive nephrectomy. Ablation of renal tumors is feasible approach and offers conservative alternatives to surgical nephrectomy. We aim to describe our institutional experience in patients undergoing renal tumor microwave ablation (MWA).

Materials and Methods: Institutional review board approval was obtained for all aspects of our study. A retrospective data retrieval and review of electronic medical records for all patients undergoing MWA of RCC was carried out. Data for patients’ characteristics, procedures, pathology, and immediate postablative and follow-up outcome parameters were recorded. Data are expressed as percentages for categoric variables and median (25th and 75th percentile interquartile range [IQR]) for continuous variables. The Kaplan-Meier method used to estimate failure rates using immediate complications, reablation, and nephrectomy procedures as endpoints.

Results: A total of 40 patients (30 men and 10 women) underwent the MWA procedure for 41 RCCs (grade T1a tumors) between 2016 and 2021. The mean age of the patients was 70 years. Patients had two comorbidities on an average with hypertension being the most common in more 78% of the patients. Of these patients, 69% had a glomerular filtration rate (GFR) less than 60, and 15% had a GFR below 30. The median nephrometry score of the tumors was 6. Biopsy showed clear cell type in 26, papillary type in 12, chromophobe type in 2, and both papillary and clear cells in 1. Patient had a minimum of 1-year follow-up period with a median follow-up period of 2 years (25th and 75th percentile IQR, 1.1–2.5 years). An immediate postablation complication encountered in 1 patient with a thermal colonic injury (2.5%). Three patients (7.5%) experienced recurrence requiring either additional ablation or nephrectomy procedures. The overall survival rates at 2 and 4 years were 90% (95% confidence interval, 75–96).

Conclusions: Percutaneous MWA of is valuable and offers safe treatment option for RCC in selected patients. Preserving the renal parenchyma is particularly warranted in patients with prior nephrectomy, recurrent tumors, or high-risk morbidity or mortality from invasive resection.