Therapeutic effects of PS-K and busulfan on the recurrent and metastatic diseases after the surgical removal of 3-methylcholanthrene-induced autochthonous tumors in C57BL/6 mice.

The effectiveness of a protein-bound polysaccharide, PS-K, and an immunoaugmenting antileukemia agent, busulfan (BU), was investigated for the treatment of autochthonous tumors induced by 3-methylcholanthrene in C57BL/6 mice. PS-K and BU were found to be effective in dealing with recurrence and pulmonary metastasis when applied in conjunction with the surgical removal of the primary tumor. The survival time of mice to which PS-K (300 mg/kg/day X 5 or X 2/week for 7 weeks, ip) or BU (50 mg/kg X 3, po) was administered was significantly prolonged when compared with that of mice treated by surgery alone. Moreover, the incidence of the local recurrence of tumors was significantly lower in mice treated with PS-K or BU after the surgical removal of the primary tumor. The effectiveness of the treatment on metastasis was also shown by the prolongation of mean survival time in groups of mice which showed no local recurrence of tumors. The timing-dependency of the treatment with PS-K did not seem to be an important factor and no additive therapeutic effects of PS-K and BU were observed in the present study.