Combination therapy of continuous venous infusion (CVI) of 5-FU and low dose consecutive cisplatin (CDDP), and the new oral anti-cancer drug S-1 for advanced gastro-intestinal cancer

Highly effective treatment is required for patients with advanced GI cancer. Returning to the starting point for reconsideration of cancer chemotherapy, with the aim of attaining a therapy (self rescuing concept: SRC) with more potential efficacy and less toxicity than current therapy, we report two kinds of chemotherapy in the present paper. They were set up preclinically using the theory of 5-FU biochemical modulation, and demonstrated their usefulness in clinical practice. S-1 is a newly developed oral anti-cancer drug which is a combination of Tegafur (FT), a prodrug of 5-FU and two modulators (CDHP, an inhibitor of 5-FU degradation and Oxo, a selective inhibitor GI toxicity by 5-FU) at a molar ratio of 1:0.4:1. In combination with CDHP, 5-FU gradually released from FT remained longer in plasma, and consequently had high anti-tumor activity, while the combined Oxo significantly suppressed GI toxicity due to 5-FU. The response rate to S-1 of stomach cancer in a phase II study was 46.5% (60/129). Toxicity at more than G3 was less than 10%. In the combination therapy employing 5-FU by CVI (5-FU: 250-350 mg/body for 24 h, 4-6 wks) and low dose consecutive CDDP, CDDP acts mainly as a modulator of 5-FU (to increase 5-FU sensitivity for tumor by inhibition of intracellular Met incorporation). For this purpose, it was found that daily consecutive administration is required, even at low dose of CDDP (3-5 mg/body/day for 5 days). A high response rate (40-60%) was obtained for advanced GI cancer. Toxicity at more than G3 was less than 10%. On the other hand, the possibility has been suggested that so far as 5-FU is concerned, CVI every other day (500-750 mg/body/day for 3 days) is more favorable than long term CVI, with regard to decreasing GI and myelotoxicities based upon the difference in generation time between normal cell (GI mucous membrane and stem cell) and tumor cell cycles. The possibility is suggested that the above-mentioned chemotherapy can become a standard therapy for GI cancer.