Phase 1/2 clinical study of irinotecan and oral S-1 (IRIS) in patients with advanced gastric cancer

Background

Irinotecan and S-1, an oral fluoropyrimidine composed of tegafur, gimeracil, and oteracil potassium, have demonstrated antitumor activity against advanced gastric cancer. We performed a phase 1/2 study to determine the recommended dose, antitumor activity, and safety of a combination of S-1 and irinotecan in patients with advanced gastric cancer.

Methods

Patients with previously untreated advanced gastric cancer were enrolled. Patients received irinotecan intravenously on days 1 and 15 plus oral S-1 twice daily on days 1–14 of a 28-day cycle. In the phase 1 part, the dose of irinotecan was escalated from 100 mg/m² to 125 mg/m² and then to 150 mg/m².

Results

A total of 24 patients were enrolled. Overall, the median number of treatment cycles per patient was 5.9, and 92% of the patients completed at least two cycles. The overall response rate was 54.2% (13 of 24). The response rates in differentiated and undifferentiated cancer were 56.3% (nine of 16) and 50.0% (four of eight), respectively. Median survival time was 581 days. The maximum tolerated dose of irinotecan was not reached at the highest level. However, grade 4 neutropenia occurred at 125 mg/m². We concluded that the recommended dose of irinotecan for the present regimen was 125 mg/m².

Conclusion

Treatment with S-1+irinotecan is considered effective in patients with advanced gastric cancer who have not previously received chemotherapy. A combination of irinotecan and S-1 was well tolerated in patients with advanced gastric cancer and could be given on an outpatient basis.