Microwave ablation

Table 2.2.1. Microwave ablation compared to radiofrequency ablation...

Simon CJ, Dupuy DE, Mayo-Smith WW (2005) Microwave ablation principles and applications. Radiographics 25 [Suppl 1] S69-S83... 

Wright AS, Lee FT Jr, Mahvi DM (2003) Hepatic microwave ablation with multiple antennae results in synergistically larger zones of coagulation necrosis. Ann Surg Oncol 10 275-283... 

Wright AS, Sampson LA, Warner TF, Mahvi DM, Lee FT Jr (2005) Radiofrequency versus microwave ablation in a hepatic porcine model. Radiology 236 132-139... 

Microwave ablation is the most recent development in the field of tumor ablation. The technique allows for flexible approaches to treatment, including percutaneous, laparoscopic, and open surgical access (Simon et al. 2005). 

Shiina S, Teratani T, Obi S, Hamamura K, Koike Y, Omata M (2002) Nonsurgical treatment of hepatocellular carcinoma from percutaneous ethanol injection therapy and percutaneous microwave coagulation therapy to radiofrequency ablation. Oncology 62 64-68 Simon CJ, Dupuy DE, Mayo-Smith WW (2005) Microwave ablation principles and applications. Radiographics 25 [Suppl 1] S69-S83... 

Recently there has been great interest in the further developments of interstitial procedures such as laser-induced interstitial thermotherapy (LITT), RF ablation, and microwave ablation and cryotherapy. 

One of the image-guided percutaneous modalities is microwave ablation in lung cancer showing marked effect with minimum tissue trauma. The overall response rate in one of the studies reached 57.1% without sideeffects or complications (Feng et al. 2002). Complete tumor necrosis was proven by biopsy. 

Microwave Ablation Therapy 226 Cryotherapy 226 Summary 229 References 229... 

These include mainly thermal ablative techniques such as laser-induced thermotherapy, radiofrequency and microwave ablation, but also chemoembolization as well as selective internal irradiation therapy. 

The technique, patient selection and main complications are similar to those for radiofrequency and laser ablation. The procedure is usually guided with ultrasound or CT. Microwave treatment produces coagulation within 60 s at a power setting of 60 W. However, the area of coagulation is smaller than that achieved after laser or radiofrequency and it is necessary to repeat the treatments several times a week in order to achieve a sufficiently large area of tumour necrosis. As with RF ablation, occlusion of segmental hepatic blood flow has been used with microwave ablation in the treatment of hepatocellular carcinoma to increase the size of the ablative lesion (Ishida et al. 2002). The use of multiple antennae is another technique, which has been described to achieve an increased volume of tumour necrosis (Wright et al. 2003 Xu et al. 2004). 

Dong et al. (2003) report a 5-year survival of 56.7% in 234 patients with hepatocellular carcinoma treated with microwave ablation therapy. Shibata et al. (2002b) compared RF and microwave ablation in the treatment of small hepatocellular carcinomas and found no difference in therapeutic effect or complication rates between the two techniques, although RF ablation was completed with fewer sessions. There is less evidence for the therapeutic effect of microwave ablation in patients with colorectal liver metastases. In one series of 74 patients with colorectal liver metastases a 5-year survival rate of 29% was achieved, with no major complications observed (Liang et al. 2003). At present, there is, however no substantial series of patients with hepatic metastases treated with microwave coagulation. 

Therapeutic alternatives in the treatment of liver metastases include surgery, local ablation as LITT, radiofrequency (RE) ablation, cryotherapy (Charnley et al. 1989 Finlay et al. 2000 Hewitt et al. 1998 Seifert et al. 2000 Shapiro et al. 1998), microwave ablation and ethanol injection (Bartolozzi and Lencioni 1996 Amin et al. 1993 De Cobelli et al. 1994 Livraghi et al. 1990, 1993, 1995 Shiina et al. 1990 Sironi et al. 1991) or oncologic strategies such as systemic or locoregional che-... 

Liver resection can therefore be offered only to a small number of patients with a good chance of success. There is a demand for additional treatments to improve the success of resection and to diminish the incidence of recurrence after surgery, particularly in patients for whom surgery is not an option. Alternative methods include oncologic strategies, such as systemic or locoregional chemotherapy, and interventional techniques, including percutaneous alcohol injection, transarterial chemoembolization, microwave ablation, and percutaneous laser treatment (Lin et al. 1997). 

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