Dose Finding Study of S-1, Oxaliplatin, and Irinotecan Combination Chemotherapy for Patients With Inoperable Advanced or Metastatic Gastrointestinal Cancers

Oxaliplatin or irinotecan has shown a considerable anti-tumor activity, when used in combination with 5-fluorouracil (5-FU) in patients with gastrointestinal (GI) cancer. Oxaliplatin, irinotecan, and 5-FU have different mechanisms of actions and do not share the toxicity profiles. Since they have a synergistic effect, many clinical trials have been conducted recently to evaluate the efficacy of triplet combination consisting of oxaliplatin, irinotecan, and 5-FU, and demonstrated that the triple combination regimen was effective and resulted in survival benefits with favorable toxicity profiles. S-1 and capecitabine are novel oral fluoropyrimidines and different phase III trials have shown that these oral agents are at least as active and effective as 5-FU with a superior safety profile. Biweekly triple combination of S-1 with oxaliplatin and irinotecan (OIS) is an interesting alternative to increase convenience and to simply the treatment delivery. In the present study, we attempt to determine the feasibility of OIS combination, the maximum tolerated dose and the recommended doses of the agents used, and to preliminarily evaluate the antitumor activity in untreated patients with advanced gastrointestinal cancer.