Phase II study of oxaliplatin, irinotecan and S-1 therapy in patients with advanced gastric cancer: the Korean Cancer Study Group ST14-11

Background: Doublet chemotherapy of platinum and 5-fluorouracil is a standard first-line treatment for patients with unresectable gastric cancer. Although the addition of taxane or irinotecan to this regimen has yielded promising efficacy, its use has been limited due to severe toxicities. To overcome this limitation, we evaluated the efficacy and safety of the combination of irinotecan, oxaliplatin, and S-1 (OIS) for the treatment of advanced gastric cancer. Methods: Chemotherapy-naïve patients with pathologically proven advanced gastric adenocarcinoma were assessed for eligibility. Irinotecan (135 mg/m²) and oxaliplatin (65 mg/m²) were administered intravenously on day 1, and S-1 (80 mg/m²/day) was administered orally on days 1–7 of every 2-week cycle. Results: Forty-four patients (median age 57 years) were enrolled and all but one patient had a good performance status (ECOG 0 or 1). A total of 529 cycles were administered, with a median of 9.5 (range 1–31) cycles per patient. The overall response rate was 61.4% (95% confidence interval [CI] 46.6–74.3). The median progression-free survival and overall survival were 10.8 months (95% CI 7.6–14.0) and 15.4 months (95% CI 12.6–18.2), respectively. Major toxicities included grade 3/4 neutropenia (38.6%), febrile neutropenia (13.6%), abdominal pain (9.1%), and diarrhea (9.1%). Conclusion: These data suggest that the OIS regimen is effective and relatively well tolerated in patients with advanced gastric cancer. Given that all the patients treated, but one, had a good performance status, these results must be confirmed in a patient population more representative of regular clinical practice. Trial Registration: ClinicalTrials.gov Identifier: NCT02527785.