Radiofrequency ablation: the technique
Radiofrequency (RF) ablation has been demonstrated to be effective in the treatment of non-resectable hepatic malignancies, and promising results have been observed in the treatment of kidney, lung, brain, prostate and bone tumours. The experience of RF ablation in patients with breast cancer is far more limited. A few pilot studies have been published to date.
During RF ablation, high frequency 100–500 kHz alternating current emitted from the non-insulated tip of the needle electrode (Figs 1, 2) propagates into the adjacent tissues, where it causes ionic vibration as the ions attempt to follow the rapidly changing direction of the alternating current. The tissue heats resistively in the area that is in contact with the needle electrode tip, and the heat then transfers conductively to more distant tissue.
The objective of RF ablation is to generate local temperatures that will result in tissue destruction. In general, the higher the target temperature, the less exposure time is needed for cellular destruction. It has been shown that, in the treatment of liver tumours, thermal coagulation begins at 70ºC and tissue desiccation begins at 100ºC, with resulting coagulation necrosis of the tumour tissue and surrounding hepatic parenchyma.
The use of RF ablation to treat breast tumours was initially demonstrated by Jeffrey et al., who treated five women with locally advanced invasive breast cancer (range, 4 to 7 cm in size). By their study design, only portions of the tumours were treated, so that the zone of ablation and margin separating the ablated and non-ablated tissue could be assessed. All patients underwent either mastectomy or lumpectomy after the RF ablation procedure. On the basis of these initial results, the authors conclude that RF ablation was effective in causing invasive breast cancer cell death, but would be more useful for treatment of tumours smaller than 3 cm in diameter.
Izzo et al. performed US-guided RF ablation followed by immediate resection in 26 patients with T1 and T2 breast cancers (range, 0.7 – 3.0 cm in size). They observed complete coagulation necrosis of the tumour in 25-96% of the patients. One patient had a microscopic focus of viable tissue adjacent to the needle shaft site.
Noguchi et al. studied 10 patients with breast cancer less than 2 cm in diameter. After RF ablation, wide excision was performed in seven cases and total mastectomy in three cases. The surgical margin of the tumour was negative in all of the seven patients who underwent wide excision.
Fornage et al. had treated 20 patients with 21 malignant breast tumours </= 2 cm. All underwent primary RF ablation. In all cases histology showed complete loss of cell viability.
In another study, Klimberg et al. reported 41 patients who underwent mastectomy (group I 22 patients) or lumpectomy (group II 19 patients) followed by RF ablation of the operation cavity as a means to achieve negative margins at the first operation (Fig 3). The cavity, with surrounding tissue, was resected and underwent histopathologic examination. No in site local recurrences have occurred during a median follow up of 24 months.
RFA in breast tissue is feasible. There is potential that thermal ablation might replace lumpectomy in small breast cancer in the future; however, this has to be confirmed in further studies.
For references contact: stoeckel.@medinf.mu-luebeck.de