'Skipping' is still a problem with radiofrequency ablation of small renal tumours

OBJECTIVE To evaluate the homogeneity and extent of necrosis obtained with next-generation radiofrequency ablation (RFA) equipment and techniques, as incomplete tumour necrosis, or 'skipping', has been documented after RFA of renal tumours and subsequent partial nephrectomy, but this was assumed to result from insufficient energy deposition with first-generation low-energy generators. PATIENTS AND METHODS In all, 17 patients with solitary renal tumours of <= 4 cm were treated with RFA under laparoscopic control. A state-of-the-art monopolar RFA generator and 15 G multi-tined needle probes were used. The probe tines were deployed to create an ablation zone > 0.5-1.0 cm beyond the sonographically controlled tumour borders. Target temperatures of 105 degrees C were applied in three cycles for 10-30 min at up to 150 W. Tumours were then removed by laparoscopic partial nephrectomy and specimens evaluated by detailed histology. RESULTS The mean (range) resected tumour size was 22 (11-40) mm, the mean RFA time was 39 (27-59) min and the mean surgical resection time was 25 (12-45) min. In 13 patients, haemostasis was sufficient to avoid the renal pedicle being clamped. Intraoperative repeated positive margins in one patient required a laparoscopic radical nephrectomy. Thirteen (76%) renal masses showed histologically complete ablation of the entire tumour. Of the four RFA failures, three tumours were > 3 cm in diameter, two were highly vascularized and three had a very heterogeneous tissue texture. CONCLUSIONS Even with state-of-the-art technology, skipping remains a problem with RFA for small renal masses and renders the technique unreliable.