Radiofrequency ablation of incidental benign small renal mass: outcomes and follow-up protocol

Objective: To review our 10-year experience with radiofrequency ablation, focusing on the outcomes for the incidental benign renal tumor. Tumor ablation is an alternative minimally invasive approach for the treatment of small renal masses (SRMs), with published series appropriately emphasizing the outcomes for the renal cell carcinoma subset of treated tumors. However, just as with partial nephrectomy, approximately 20% of SRMs are benign. The intermediate- to long-term outcome of the incidentally ablated benign tumor and its appropriate follow-up protocol is unknown.

Methods: All SRMs treated with temperature-based radiofrequency ablation from 2001 to 2011 were reviewed. Of a total of 280 enhancing SRMs biopsied at radiofrequency ablation, 47 were confirmed as benign tumors. Ablation success was defined as the lack of enhancement on the initial postablation axial imaging. Recurrence was defined as tumor growth and enhancement on follow-up axial imaging.

Results: Of the 47 benign tumors, 32 were treated percutaneously and 15 laparoscopically. The histologic biopsy finding was angiomyolipoma in 10 and oncocytoma in 37. The median tumor size was 2 cm (range 1-3.6), and the mean follow-up was 45 months. No recurrences developed, and all lesions required only 1 treatment session. The median pre- and postoperative glomerular filtration rate was 77 mL/min/1.73 m(2) (range 39-137) and 68 mL/min/1.73 m(2) (range 36-137). The present study was limited by its retrospective nature and small sample population.

Conclusion: Radiofrequency ablation of SRMs <3.5 cm found to be benign on concurrent biopsy can be efficaciously treated with a single treatment session. Long-term follow-up imaging might not be required if successful ablation is determined at the initial post-treatment cross-sectional imaging study.