脳腫瘍の非手術的療法 microwave 照射による効果

抄録

There have been reports concerning an application of hyperthermia for the treatment of malignant tumors. To raise the local temperature of a tumor, microwave irradiation was used for its local heat effect in deeper structure.
Yoshida sarcoma cells were transplanted subcutaneously into bilateral hind limbs of rats. Tumors on the left side were heated to 42°C for 30 min, by exposure to 2450 MHz microwave, while body temperture was kept below 37°C throughout the treatment. Immediately after microwave irradiation,3H-thymidine was given intraperitonealy to rats. Tumors on the right side were served as a control without microwave irradiation and 48 hrs. later animals were sacrificed. Samples were oxidized by Tri-Carb. autosample oxidizer and radioactivity was measured by a liquid scintillation counter. In irradiated group, the percent ratio of disintegration per minute per mg weight of the irradiated tumor versus that of the non-treated was 48.1±18.1, i. e., an uptake of 3H-thymidine was markedly suppressed by microwave irradiation. In the non-treated group, there was no significant difference in 3H-thymidine uptake between the tumors on the right side and these on the left. However, microwave irradiation did not apper to affect significantly the size and weight of tumors. Histologically, it seemed that there was more prominent necrosis in the treated tumor than in the non-treated, which may be a histological manifestation of the decreased thymidine uptake.
Further studies using experimental brain tumors in rabbits were performed. VX-2 carcinoma was transplanted into the right frontal lobe, and on the 5th and 7th days tumors were heated to 42°C for 2hrs, by exposure to microwave. During microwave irradiation, local temperature was monitored by an epidural thermister needle. Evans' blue solution was intravenously given immediately after microwave irradiation and rabbits were sacrificed on the 3rd or 7th day after treatment with microwave. These animals showed clinical evidence of tumor ghowth;increasing irritability, loss of appetite, and even lethargy, and these signs were remarkably slight in the microwave irradiated group. Macroscopic examination revealed that the size of tumor was much larger in the non-irradiated group than in the irradiated. Tumors of the non-irradiated group were stained uniformly with Evans' blue on the 10th day, and small dark brown spots were scattered on the 14th day. In the irradiated group dark brown areas, which were confirmed to be necrosis microscopically, occupied most part of the tumor and occasional blue stain was noted around those areas as early as on the 10th day. On the 14th day there was a small tumor mass growing next to the necrotic area. Histologically, the tumor was densely cellular with small foci of necrosis on the 10th day and the areas of necrosis became large and abundant and various stages of degenerative changes were noted in the cells surrounding the foci of necrosis on the 14th day in the nonirradiated group. In the irradiated group, much larger areas of necrosis were noted and tumors were entirely necrotic in one third of the irradiated on the 10th day after transplantation. In addition to a large extent of necrosis, the pattern of various stages of cell degeneration surrounding the necrosis was not seen, which were typically recognized in the non-irradiated tumor. Edematous changes of the surrounding brain tissue were marked in the irradiated group, and even disappearance of adjacent nerve cells was noted in some cases. However, microwave irradiation of normal brain tissue has no such effect.