Percutaneous Ablation Techniques / Radiofrequency ablation (RFA)
Another route to treat primary and secondary solid organ tumours is via direct ablation (using thermal energy to destroy cells and cause tumour necrosis.) This is an evolving technique and has been used in liver, renal and lung tumours with some success.
Liver ablation techniques
Percutaneous Ethanol Injection (PEI) was an early technique involving the injection of absolute ethanol (alcohol) directly into HCC lesions under ultrasound control and achieved satisfactory results in small tumours <3cm. [16] Other techniques that have been used include cryoablation (freezing of tumours), microwave ablation, and laser techniques, but radiofrequency ablation (RFA) remains the predominant technique. [17] RFA has been approved by NICE (National Institute of Clinical Excellence) for the treatment of unresectable HCC and colorectal hepatic metastases. [18]
RFA – Mechanism of action
RFA produces movement of ions in the tissue which results in heating and cellular death. Heating to a temperature of 60-100 oC results in almost immediate tissue damage.
RFA is based on producing tissue necrosis using a high-frequency alternating current that is delivered through an electrode placed in the centre of the tumour [19, 20]. Tissue necrosis begins as the temperature approaches 60°C, and RFA treatments often result in local tissue temperatures that approach or exceed 100°C, which result in tumour cell death.
It is possible to treat single tumours of up to 5 cm in diameter, and multiple tumours of <3cm diameter.
Technique of RFA
Figure a – Small peripheral liver tumour in right lobe of liver (black arrow) pre-ablation
Figure b – Intraoperative CT image of RFA needle in position within lesion (white arrow)
Figure c – Post RFA CT image demonstrating tumour necrosis (white arrow)
Restrictions to the use of RFA
Complications of RFA
Is RFA the preferred treatment?
Despite many published reports of RFA in HCC and liver metastases, large scale randomised trials comparing RFA, TACE and SIRT in the treatment of these tumours are still awaited. It is not easy to clearly state which treatment is best for each tumour size and distribution, and multidisciplinary discussion between oncologists, surgeons and interventional radiologists is the best approach to determining the best course of treatment.