Modification of spontaneous lung metastasis by local radiation combined with or without immunomodifier

This study was carried out to determine the effect of local irradiation of the NFSa tumors on the incidence of lung metastases. The spontaneous lung metastases were found in those animals whose tumors had grown in size bigger than 10 mm in diameter. The incidence of metastases and the number of lung nodules were increased in those animals of irradiated group when compared to those of control group with the same size. This is probably because the irradiation of tumors resulted some retardation in their growth and thus, the irradiated tumors took a longer time to reach a given size than those unirradiated control tumors. The incidence of spontaneous lung metastases was significantly reduced by subcutaneous administration of OK-432 (2.5KE/mouse) locally into the surroundings of the tumor immediately after irradiation. The administration of OK-432 after the metastasis development was no longer effective. Both of intraperitoneal and subcutaneous administrations of OK-432 into opposite side of unirradiated thigh showed no suppression of metastasis. These results suggest that an appropriate immunostimulation combined with radiotherapy may be important for the suppression of tumor metastases.