Purpose: The Japanese Foundation for Multidisciplinary Treatment of Cancer conducted a Phase I study of a novel oral fluorouracil derivative, S-1, combined with a low dose of cisplatin in unresectable and recurrent gastric cancer.
Experimental design: S-1 was administered orally at 80-120 mg/body/day, depending on body surface area. One course consisted of consecutive administration for 28 days followed by a rest of 14 days. Low-dose cisplatin was given i.v. on days 1-5, 8-12, 15-19, and 22-26 of each course. The dose escalation of cisplatin began with an initial dose of 1 mg/m(2)/day as level 1 and was stepped up to 2, 3, 4, and 6 mg/m(2)/day as level 2, 3, 4, and 5, respectively. The regimen was repeated for at least two courses.
Results: A total of 24 patients was entered in the study. There was no treatment-related death. At level 5, consisting of 5 evaluable patients, dose-limiting toxicity was experienced as grade 3 appetite loss in 2 patients and grade 4 neutropenia in 1 patient. The maximum-tolerated dose of cisplatin was estimated to be 6 mg/m(2)/day. We decided on a recommended dose of cisplatin of 4 mg/m(2)/day because the dosage was one level under the maximum-tolerated dose. All 3 patients at level 4 showed partial response, suggesting promising clinical efficacy with this dosage. The serum concentration of cisplatin at level 4 was 918 +/- 92 ng/ml on day 26 of the first course.
Conclusions: S-1 with low-dose cisplatin may become an effective regimen with acceptable toxicity for gastric cancer.