Experimental radiology for prevention and control of metastasis

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The present study aimed to obtain basic infomaiton, which could be useful in clinical situation. The processes of hematogenous metastasis can be divided into three steps,i.e., tumor cell release from the primary into the blood circulation, transportation, arrest and growth at the secondary site. All of these steps are important and have to be considered in the study for prevention and treatment of metastases.In the first year, we studied effect of neutron irradiation of local tumors on clonogenic tumor cell release and metastasis formation. The results indicated neutron suppressed clonogenic tumor cell release and metastasis more effectively than X-rays. In the current year, the effect of intratumoral injection of OK432 on metastasis formation was investigated using various tumor systems including immunogenic or nonimmunogenic. Only intratumoral injection was effective in nonimmunogenic tumor systems although either i.p or i.m./s.c. in the opposite leg to the inoculated tumor was aslo effective in immunogenic tumor systems.The suppression of lung metastasis formation by intratumoral injection of OK-432 was paralleled with the reduction of clonogenic tumor cell release into the blood circulation.