We evaluated the effectiveness of radiotherapy combined with high-power hyperthermia with a radiofrequency output over 1500W for 13 patients with nonsmall cell lung cancer. An average total dose of 59.8 Gy by the conventional method, and an average of 12 sessions of hyperthermia during radiotherapy were employed. In addition, an average of 15 sessions of hyperthermia was administered after completing the radiotherapy. Complete response (CR, 100% regression) was achieved in 10/13 (77%) patients and partial response (PR, over 50% regression) in 3/13 (33%) for an overall response rate of 100%. Radiotherapy combined with high-power hyperthermia is especially advantageous for young patients with a thin subcutaneous fatty layer of the chest wall.
For deep hyperthermia using an 8 MHz radiofrequency (RF) capacitive heating device, overheating the subcutaneous fatty layer is a major problem. Increasing the cooling ability of the overlay bolus circulating liquid by the external cooling unit was carried out to prevent overheating the subcutaneous fatty layer. Using the external cooling unit, the cooling ability was significantly improved at a depth of 1.5 cm from the surface in the agar phantom experiments. In clinical studies, we increased the RF output by over 50% even in cases of a subcutaneous fatty layer over 2 cm. Increasing the cooling ability of the overlay bolus circulating liquid is considered an effective method for deep hyperthermia.
Tap water has conventionally been used as the overlay bolus circulation liquid in hyperthermia using an 8MHz radiofrequency (RF) capacitive heating device. Tap water absorbs RF thus decreasing the efficiency of deep heating. We used 0.5% NaCl as the circulation liquid to improve the efficiency of deep hyperthermia. In phantom experiments, the deep heating efficiency increased by 1.5 °C per 5 min using 0.5% NaCl and the increase of heating efficiency was about 40%. In clinical cases, 43 °C of the intraesophageal temperature was obtained by a lower output power of 180W. A higher deep-seated temperature can be obtained at an equal RF output using 0.5% NaCl for the overlay bolus circulation liquid.
The effect of magnetic force on the uptake of magnetoliposomes in tumor cells was investigated. When a magnet was placed under the cell culture dish, the magnetoliposome-uptake in the tumor cells was increased markedly. In a rat subcutaneous tumor, the uptake was also enhanced by using a magnet : the uptake ratio being 70.0% of the magnetoliposomes injected, compared to just 27.4% when no magnet was used. The magnetoliposomes can act as an internal heating material. Thus, the tumor was subjected to hyperthermia by applying an alternating magnetic field. As a result, the efficiency of heating was improved, and 90% of the tumor was necrosed