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for tumor inactivation was conducted successfully in th e leading to immediate degenerative necrosis of local tissue,
Second Department of Surgery, Kurume University Hospital which can be better evaluated using the histochemical
in Fukuoka City, Japan. Soon, successful use of microwave method. [27] MCT is non-carbonizing, non-spattering,
[11]
coagulation was reported throughout Japan, with large minimally invasive, and wound controllable. With these
[28]
patient cohorts, multiple heating sessions, treating tumors advantages, this method is now widely used in coagulation
with larger diameters, combination use with other ablation therapies including dermatology, gynecology, stomatology,
modalities, and review and management of side-effects. and otorhinolaryngology. [29,30]
[12]
A recent study reported the long-term efficacy results of
surgical MCT for the treatment of 60 cases of unresectable Cool-tip microwave therapy apparatus incorporates
HCC in the Kyushu Medical Center, National Hospital a microcomputer, which automatically operates the
Organization, Fukuoka, Japan. The 1-, 3-, and 5-year survival system. Electrical resistance, current, and power of the
[31]
rates were 93.9%, 53.8%, and 43.1%, respectively, almost the system are regulated automatically during the entire course
same as the results of palliative surgical resection. In April of treatment. The technique of cool recycling solved the
[32]
[13]
1996, MCT was included in the coverage list of Japanese problems of inappropriately high temperature in the rod
Medical Insurance, which contributed to the advancement antenna and a limited coagulation area that the conventional
in the research on MCT for the treatment of HCC in Japan. [14] microwave systems had. The new systems enhanced
[4]
the operational safety, expanded therapeutic indications,
In the 1990s, MCT was gradually accepted in other regions improved the patients’ quality-of-life, and post-operational
of the world for the treatment of HCC. [8] survival. [17,33]

BASIC PRINCIPLES MCT for the treatment of tumors is now being investigated
its potential to enhance host resistance to malignancies. This
The fundamental principle of MCT is based on the facts was resulted from reports of incidental observations showing
that tumor tissues are more sensitive to heat than the spontaneous regression of remote metastasis after thermal
[34]
adjacent normal tissues, and that microwave heat can be ablation. On one hand, microwave coagulation results
[15]
controllably delivered to the tumor tissues. Compared in irreversible coagulation necrosis of tumor cells through
[35]
with normal tissue, tumor tissues have low blood flow and the thermal effect; on the other hand, the coagulated
extra-cellular pH value, as proven by experiments showing tumor tissue that retained in the body will stimulate the
that the blood flow volume in murine HCC tissue is only 5% host to enhance its systemic immunity against cancer with
of that in normal liver tissue. When a tumor is irradiated consequent resistance to viable allogenic and heterogenic
[16]
with microwave energy, the heat will make the blood flow cancer cells. Animal experiments demonstrated that in
[36]
stagnant at the local area. When the temperature in tumor mice model of H22 implanted advanced HCC, intra-tumoral
[17]
tissue goes up to 42-45 °C, the blood flow in the tumor stops, CD8+ cells increased remarkably in the MCT group compared
cancer cells become anoxic, mitochondria in cancer cells to that in the surgery alone group. This provided supporting
show vacuolation, resulting in the cessation of intra-cellular evidence for the immune enhancement by the coagulated
respiration, apoptosis, heat fixation, and death of cells. [12,18,19] tumor tissue that retained in the local area. [37,38] Studies
showed that the local density of lymphocytes infiltration is
When the local temperature reaches 60 °C and above, tumor closely related to the prognosis of patients with some cancer,
tissues will be immediately coagulated and damaged by the that is, a higher density of intra-tumoral and peri-tumoral
[20]
effects of thermal treatment. A controllable temperature lymphocytes infiltration, like CD8+, is predictive of a better
range of 60-120 °C can be presented rapidly to the target patient outcome. [39]
area by the treatment system. During the procedure of
[21]
MCT, a specially made needle is initially inserted into the EQUIPMENT
center of tumor. The tip of the needle contains a point acting
as an emission antenna. The system includes an electric Microwave ablation system
[22]
device that produces microwave energy forming a magnetic At present, the MCT systems with water-cool shaft or antenna
field around the point of the antenna. The magnetic field are more commonly used in the clinic for the treatment of
[23]
makes nearby molecules spin and vibrate in very high velocity HCC. [4,25] All systems are equipped with flexible low-loss
with resultant hyperthermia in the local area. [24,25] This is power cables and a surface coating microwave antenna
called the thermal effect of microwave antenna radiation. of 15 gauges. [7,40] The tip of the needle-like antenna is not
[26]
[7]
Because energy density is very high in the area, protein will insulated and is exposed to the tissue to be ablated.
be coagulated by the heat swiftly in the contacted tissues Electromagnetic microwaves are emitted by the microwave

160 Hepatoma Research | Volume 1 | Issue 3 | October 15, 2015