Combined effect of S-1 and CDDP as a modulator for colon 26 liver metastasis

S-1 is a novel oral anticancer drug, composed of tegafur (FT), gimestat (CDHP) and otastat potassium (Oxo) in a molar ratio of 1:0.4:1, based on the biochemical modulation of 5-fluorouracil (5-FU). In this study the combined effect of S-1 and low-dose CDDP as a modulator for colon 26 liver metastasis in mice was evaluated. In an experiment with S-1 (5 mg/kg/day: po) and CDDP (0.25 mg/kg/day: i.p.) for 14 days, the combined effects for both liver metastasis and tumor of spleen were not superior to those with S-1 or CDDP alone group. Body weight loss was not greater in the S-1 + CDDP group than in the control group. In an experiment with S-1 (5 mg x 2/kg/day: po) and CDDP (0.25 mg/kg/day: i.p.) for 7 days, the inhibitory effects of S-1 + CDDP of liver metastasis and tumor of the spleen were remarkable compared with the S-1 alone group. However a greater loss of body weight was seen in the S-1 + CDDP group than in other groups. This study suggests that low-dose CDDP might be a modulator of S-1 for colon 26 liver metastasis. Further study is needed to determine the optimum dose and duration of treatment.