New Approaches to the Treatment of Hepatic Malignancies
Other Thermal Ablation Techniques: Microwave and Interstitial
Laser Ablation of Liver Tumors
Francesco Izzo, MD
Background: Thermal ablation of hepatic malignancies is becoming a widespread treatment
approach. In addition to radiofrequency ablation, microwave coagulation (MCT) and laser-induced
interstitial thermotherapy (LITT) are being used clinically to treat patients with liver cancers.
Methods: The principles and clinical indications for MCT and LITT are described. Treatment
approaches and results from published clinical studies are reviewed. The evolution of these thermal
treatment modalities and limitations of currently available equipment is provided.
Results: The interstitial probes and equipment used for MCT and LITT for liver tumors are
undergoing changes to improve treatment efficacy. Both MCT and LITT have been limited by the
relatively small zone of coagulation produced with a single probe placement. Both techniques can
be performed safely, and local recurrence and long-term survival rates are being established.
Conclusions: MCT and LITT are two alternative thermal ablation techniques being used to treat
patients with primary and metastatic hepatic malignancies. The utility of these two treatments has
been limited by the relatively small area of thermal necrosis produced around the interstitial probes,
but design modifications and new equipment may improve these limitations.
Key Words: Microwave—Laser therapy—Liver cancer—Thermal ablation.
MICROWAVE COAGULATION THERAPY FOR
Background and Principles of Microwave
Microwave coagulation was initially developed in the
early 1980s to achieve hemostasis along the plane of tran-
section during hepatic resection.
of tissue surfaces was slower than electrocautery units and
produced deeper areas of tissue necrosis. Although micro-
wave coagulation has not been useful during hepatic resec-
tion, the extended area of tissue necrosis led to investigation
of the use of microwave coagulation therapy (MCT) to treat
unresectable hepatic malignancies.
The microwave generators developed for MCT pro-
duce microwaves with a frequency of 2450 MHz and a
wavelength of 12 cm.
Biologically, microwaves applied
to living tissues produce dielectric heat by stimulation of
water molecules within the tissue and cells. The rapid
agitation of water molecules within cells and tissues with
direct application of microwaves produces rapid fric-
tional heating and coagulative necrosis. The microwave
generators available for clinical use have an output of
70–90 watts. The microwave-emitting needle (14–22
gauge) is placed directly into the hepatic tumor to be
treated, usually using ultrasonographic guidance. The
microwave-emitting needle is attached to the microwave
generator, the generator is activated, and each area of the
tumor is treated for 30–60 seconds at 70–90 watts of
power. The rapid generation of heat using MCT produces
10- to 25-mm zones of coagulative necrosis after only
30–60 seconds. The lesions can range from spherical to
elliptical in shape. The rapid development of coagulative
necrosis within the tissue around the MCT needle pro-
Received July 18, 2002; accepted August 15, 2002.
From The G. Pascale National Cancer Institute, Naples, Italy.
Address correspondence and reprint requests to: Francesco Izzo,
MD, Via A Manzoni #52, Naples 80122, Italy; Fax: 39-081-5903-843;
Published by Lippincott Williams & Wilkins © 2003 The Society of Surgical
Annals of Surgical Oncology, 10(5):491–497