Microwave Interstitial Hyperthermia with Ablation Concept Based on the Heating and Clinical Results of Five Cases

• Published in: Thermal Medicine Vol. 24; no. 3; pp. 101 - 111
• Main Authors: AOYAGI, YUTAKA, SAITO, KAZUYUKI, HORITA, HIROTOSHI, ITO, KOICHI, TANAKA, HIROTOSHI, TATSUNO, SATOSHI, MIIDA, KAZUO, SHIMIZU, SAKURA, KANEHIRA, CHIHIRO
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society for Thermal Medicine 2008
• Subjects: coaxial-slot antennas; microwave interstitial hyperthermia; spherical SAR distribution; thermal ablation; thermal coagulation
• ISSN: 1882-2576; 1882-3750
• DOI: 10.3191/thermalmed.24.101

Interstitial hyperthermia using a single antenna would reduce invasiveness and expand indications. We developed an antenna with a nearly spherical temperature distribution, which is the ideal temperature distribution for single-antenna heating that matches the shape of common tumors. We also developed a means of inserting the antenna so that the center of the spherical temperature distribution matches that of the tumor. By increasing the antenna output, we considered the central region of the tumor could undergo thermal ablation while the peripheral region could be exposed to hyperthermia. Five patients were treated using microwave interstitial hyperthermia and radiation therapy with intent to cure. Four patients had supraclavicular or inguinal node metastasis, and one patient had a soft palate primary lesion. The mean follow-up time was 2 years and 2 months. The heated region was controlled in all patients during follow-up without evidence of tumor re-growth, in spite of the sizable tumors (3-7 cm, mean 4.5 cm). Only one antenna was inserted into three patients. In all sessions with these three patients, the antenna output was set at 10-15 W (high) per antenna, which increased the temperature of the tissue near the antenna to 47-66°C. Coagulation necrosis should have occurred at this temperature range over a wide area around the tumor center in all three patients. The advantages of single-antenna interstitial hyperthermia are as follows : 1) it is less invasive than multiple antennas, and the indications are expanded. 2) from the viewpoint of combined radiotherapy, local control rates increase because the hypoxic radioresistant region at the tumor center can be ablated more effectively and 3) it can be safely applied when ablation is contra-indicated, such as when a tumor is adjacent to nerves, vessels or healthy skin, because the temperature in the tumor periphery is lower. Interstitial hyperthermia with a single antenna is a "thermal therapy" that acts as both hyperthermia and ablation due to a longer period of heating and higher output power.