[Combination therapy of local administration of OK-432 and radiation on a murine fibrosarcoma (NFSa)--combination effect and histological examination].

The combined effect of radiation with local administration of OK-432 was studied using natural fibrosarcoma (NFSa) of C3H mice that are less immunogenic and resistant to radiation (TCD 50, 83, 15 Gy). When 2KE of OK-432 was administered together with 1 X 10(6) tumor cells, tumor survival was inhibited in 7/8 (87.5%) of mice. Single local administration of OK-432 (2KE, 4KE, 8KE) showed hardly any effect on tumor survival. Combined treatment of 2KE of OK-432 and 4-Gy radiation, however, not only controlled tumor growth but also eradicated 1/5 (20%) of them, compared with single application of 45-Gy radiation. OK-432 worked most effectively when administered just before or after the application of X-rays. The optimum dose of OK-432 was studied by administering 2KE, 4KE and 8KE of the agent together with the application of 55-Gy radiation. 8KE groups showed the best eradication rate but 4KE groups showed the best cure rate. Therefore, the optimum dose was considered to be between 4KE and 8KE. With regard to histological effects, both the single radiation treatment and its combined treatment with OK-432 were most effective on the 6th day. The degree of degeneration and necrosis of tumor cells together with lymphocyte exudation were much higher in the combined treatment than in single radiation application.