Ultrasound-guided percutaneous radiofrequency ablation of small renal tumors: Clinical results and radiological evolution during follow-up

BACKGROUND: Treatment of small renal masses with percutaneous radiofrequency ablation (RFA) is under development. Data are limited regarding the oncologic efficacy and complication rates of ultrasound (US)-guided RFA. PURPOSE: To retrospectively analyze results and factors predictive of incomplete ablation and local recurrence in patients treated for small renal tumors with US-guided percutaneous RFA. MATERIAL AND METHODS: Forty-one consecutive patients (27 males), mean 70 (40-86) years, with 44 tumors were included. Core biopsies were obtained before treatment. Follow-up was performed with CT or MRI. Tumor diameter, tumor volume, volume of the ablation zone, necrosis index, tumor location, distance from tumor to skin, and BMI were analyzed. RESULTS: Biopsies showed malignancy in 72%, 10% were benign, and 18% were inconclusive. Thirty-six tumors (82%) were completely ablated after first RFA and 40 tumors (91%) after a second treatment. Mean follow-up was 27 months. Nine completely ablated tumors (23%) showed local recurrence during follow-up, six of them were retreated. Tumor size was significantly larger and mean necrosis index lower in tumors with incomplete ablation compared with those completely ablated initially. In tumors <30 mm, the initial complete ablation rate was 93% and the local recurrence rate during follow-up was 16% (4/25). CONCLUSION: US guidance is feasible for RFA of small renal tumors. However, thorough long-term follow-up appears mandatory, as a substantial proportion of the patients will develop late local recurrence and will need more than one RFA treatment session. Large tumor diameter and volume and a low necrosis index were predictive indicators of incomplete ablation after the first treatment.