[Experimental studies on growth inhibition and regression of cancer metastases]

The most important target in pharmaceutical therapy against cancer is complete suppression of metastases and recurrence after curative surgical operation. It is fundamentally, a growth inhibition and regression of small number of autochthonous tumors scattering in the host, and coexistence between tumor and host is also important. As immunosuppressive anticancer drugs have detrimental effects for patients in such cases, application of strong immunopotentiators such as lentinan should be expected. Lentinan showed a prominent effect on suppression of metastases in experimental systems of clinical models using MH-134 hepatoma, Madison-109 lung carcinoma and DBA/2.MC.CS-1 fibrosarcoma. Suppression of carcinogenesis may be considered as one of experimental methods to prevent metastases in a viewpoint of regression of small number of autochthonous tumor cells. Lentinan given at suitable timing and schedule showed marked prophylactic effect on chemical and viral carcinogenesis. Mode of action of lentinan as T-oriented adjuvant in its antitumor and metastases-inhibitory effects is also discussed. Considering excellent end-point results of Phase III with advanced and recurrent gastrointestinal cancer, lentinan is the most hopeful substance to prevent micrometastases.