[Potentiation of combination effect of cisplatin and radiation--application of biological response modifiers]

The combination antitumor effect of three kinds of biological response modifiers (lentinan, PSK and juzentaiho-to) was evaluated in the treatment of IMC solid carcinoma with CDDP (9 mg/kg) and/or radiation (1000 rad). Remarkable antitumor effects were observed in the lentinan (2 mg/kg, daily) group to which a single dose of CDDP was given 24 hours before irradiation. On the other hand, combined therapy with CDDP and radiation alone showed less antitumor effect. No antitumor effect was observed in the groups treated with biological response modifiers (BRM) alone. Winn's test was performed to investigate the level of immunity on each treatment group. Mice were inoculated with the admixtures of immunized spleen cells and IMC carcinoma cells at a ratio of 200:1. Tumor growth was completely suppressed in the groups of CDDP and lentinan with or without radiation even on the 41st day after inoculation. These results are strongly suggestive of potentiation of the immunity of tumor bearing mouse by the combined use of lentinan. Histopathological evaluation also revealed a potent antitumor effect of combined use of lentinan. Since host immunity is known to be suppressed in the tumor bearing state, combined use of BRM in chemo-radiotherapy must play an important role in the treatment of malignant tumor.