Background: We designed an outpatient regimen consisting of fractional cisplatin in combination with S-1, a novel oral fluoropyrimidine derivative for the treatment of recurrent or advanced gastric cancer and conducted a phase I study to determine the dose limiting toxicities (DLTs) and recommended dose (RD).
Methods: Escalating dosages of cisplatin (15, 20, and 25 mg/m(2), as levels 1, 2, and 3, respectively) were administered over 2 h on days 1, 8, and 15, with a fixed dose of S-1 for 3 consecutive weeks (days 1-21), repeated every 5 weeks. National Cancer Institute common toxicity criteria(NCI-CTC) grade 2 toxicities required treatment delay. Primary first cycle DLTs were defined as NCI-CTC grade 3 or 4 toxicities (except for hemoglobin levels, nausea, and vomiting).
Results: Nine patients were initially enrolled, and DLTs did not appear; however, one level-3 patient experienced grade 3 anemia. An additional three patients were enrolled in level 3 to confirm the toxicity profiles, and none experienced DLTs. Toxicity evaluations throughout a total of 62 cycles revealed that grade 1 or 2 hematological toxicities were common, although mostly transient, with recovery without specific treatment. One patient each in levels 1 and 3 required hospitalization due to grade 3 toxicities in the later cycles. Mean dose intensities for S-1 and cisplatin were both more than 91%. There were no treatment-related deaths. The preliminary response rate was 44%.
Conclusions: It was concluded that the RD of cisplatin in this regimen was 25 mg/m(2) (level 3). S-1 in combination with fractional cisplatin is a promising regimen that allows repeated drug administration, in an outpatient setting, for advanced or recurrent gastric cancers. A phase II study of the RD is now under way.