Challenge for a better combination with basic evidence.

5-Fluorouracil (5-FU) has been the most widely accepted and studied chemotherapeutic agent, and many combination chemotherapeutic regimens have been reported. However, until recently, a standard regimen for metastatic gastric cancer had not been established. The combination of S-1 and cisplatin is a good candidate as a standard first-line regimen for metastatic gastric cancer. On the other hand, interest in biochemical modulation has become wide spread recently. The low level of dihydropyrimidine denhydrogenase (DPD), thymidylate synthase (TS) activities, and a high level of orotate phosphoribosyl-transferase (OPRT) activity enhance the antitumor effect of 5-FU and S-1. Docetaxel is one of the agents that modulate these enzyme expressions and activities. Moreover, the response rate of combination therapy of docetaxel and S-1 for metastatic gastric cancer was 56.3% and median survival time was 14.3 months in a phase II study, showing it to be a good candidate for a new standard regimen for gastric cancer. A phase III collaborative study, START (S-1 and Taxotere for advanced gastric cancer randomized phase III trial), is now under way in Japan and Korea.