[Photoradiation therapy of experimental brain tumor]

Malignant tumors retain hematoporphyrin to a much greater extent than do normal tissues and can be destroyed by exposure to light. To utilize this mechanism in the treatment of malignant brain tumor, we investigated the antitumor effect of photoradiation on rat and mouse glioma, utilizing hematoporphyrin administration and cold light irradiation. In vitro study of rat glioma (EA285), the tumor cells which were exposed to hematoporphyrin and light irradiation showed marked degeneration in a short time, though no change was found in the control groups of hematoporphyrin administration alone and of light irradiation alone. The subcutaneously transplanted gliomas of rat and mouse also showed the growth inhibition after treatment of hematoporphyrin and light irradiation, though they grew up again. Histological degeneration by this treatment reached about 7 mm depth in the tumor. It was made clear that the effect on gliomas was induced by photosensitization and not by heat. From these results it is concluded that photoradiation therapy would be a great means for adjuvant therapy for malignant brain tumor.