Microwave ablation is a process that uses the heat from microwave energy to kill cells. When used in the treatment of liver cancer, the energy is applied directly to the tumour through a special needle electrode.

The National Institute for Health and Clinical Excellence is examining microwave ablation of hepatocellular carcinoma and will publish guidance on its safety and efficacy to the NHS in England, Wales, Scotland and Northern Ireland. The Institute’s Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisers, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about microwave ablation of hepatocellular carcinoma.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

• comments on the preliminary recommendations
• the identification of factual inaccuracies
• additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows.

The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.

The Advisory Committee will then prepare draft guidance which will be the basis for the Institute’s guidance on the use of the procedure in the NHS in England, Wales, Scotland and Northern Ireland.

• For further details, see the Interventional Procedures Programme manual, which is available from the Institute’s website (www.nice.org.uk/ipprogrammemanual).

Closing date for comments: 19 December 2006
Target date for publication of guidance: March 2007

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

Current evidence on the safety and efficacy of microwave ablation of hepatocellular carcinoma appears adequate to support the use of this procedure provided that the normal arrangements are in place for consent, audit and clinical governance.

Patient selection should be carried out by a multidisciplinary team that includes a hepatobiliary surgeon.

Hepatocellular carcinoma is the most common type of primary liver cancer. For most patients, treatment with curative intent is not usually possible. The treatment options available include surgical excision, hepatic artery infusion chemotherapy, trans-arterial chemoembolisation, percutaneous ethanol injection, cryoablation, and radiofrequency ablation. Liver transplantation (with a curative intent) may be appropriate for some patients.

Microwave ablation destroys tumour cells by heat, resulting in localised areas of necrosis and tissue destruction. The procedure can be performed under local or general anaesthesia.

Under appropriate imaging guidance, needle electrodes are advanced into the liver tumour(s) during laparotomy or laparoscopy, or percutaneously, and are attached to a microwave generator. Microwave energy is then delivered to destroy areas of the tumour. Multiple pulses of energy can be delivered during one session, and multiple needle electrodes can be used to treat larger tumours.

A non-randomised controlled study of 89 patients found that overall survival was similar in patients treated by microwave ablation or liver resection at 25 months’ follow-up; local recurrence occurred in 8% of patients treated with microwave ablation (3/38) or resection (4/51). In another non-randomised controlled trial of 43 patients with well-differentiated liver tumours, overall 5‑year survival was similar after microwave ablation (70% in 23 patients) or percutaneous ethanol injection (78% in 20 patients). In the same study, 5‑year survival in patients with moderately or poorly differentiated tumours was significantly higher after microwave ablation (78% in 25 patients) than after percutaneous ethanol injection (35% in 20 patients) (p = 0.03). One case series of 288 patients who received microwave ablation reported overall survival of 51% at 5 years.

In a non-randomised controlled study of 102 patients, the mean duration of disease-free survival was 15.5 months in patients treated by microwave ablation (95% confidence intervals [CI] 11.3 to 20.0 months) compared with 16.5 months (95% CI 10.1 to 19.2 months) in those receiving radiofrequency ablation. The difference was not statistically significant (p = 0.53).

The Specialist Advisers stated that this was a novel procedure but that there were no major concerns about efficacy. They noted that data on long-term survival are limited.

A non-randomised controlled trial of 89 patients found no difference in the incidence of intra-abdominal bleeding, gastrointestinal bleeding, biliary stenosis and wound dehiscence between patients treated by microwave ablation and those treated by liver resection.

Another non-randomised controlled trial reported that major complications (not otherwise described) occurred in 8% (4/49) of patients treated by microwave ablation, and 6% (3/53) of patients treated by radiofrequency ablation (p = 0.71). A case series reported that acute respiratory distress syndrome occurred in 19% (4/21) of patients treated by open microwave ablation.

The Specialist Advisers listed the theoretical adverse events as including liver abscess, intra-peritoneal haemorrhage, neoplastic seeding, biliary peritonitis, bowel perforation, adjacent vessel thrombosis and the potential for collateral thermal injury.

The Institute has published interventional procedures guidance on radiofrequency ablation of hepatocellular carcinoma (www.nice.org.uk/IPG002) and laparoscopic liver resection (www.nice.org.uk/IPG135). The Institute will issue guidance on the use of microwave ablation for metastases of the liver (www.nice.org.uk/ip_381).

Bruce Campbell

Chairman, Interventional Procedures Advisory Committee

December 2006

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

‘Interventional procedure overview of microwave ablation for primary and secondary liver cancers’, August 2006.

Available from: www.nice.org.uk/ip370overview.