Phase i study of neoadjuvant chemoradiotherapy with S-1 and oxaliplatin in patients with locally advanced gastric cancer

Purpose The aim of this phase I study was to investigate the optimal dose of S-1 and oxaliplatin with concurrent radiotherapy in a preoperative setting for locally advanced gastric cancer. Patients and methods Twelve patients with histologically confirmed clinical stage T2N+ or T3-T4 gastric adenocarcinoma received dose level -1 (oral S-1 at 60 mg/m ²/ day + oxaliplatin 40 mg/m ² intravenously on days 1, 8, 15 and 22) or dose level 1 (S-1 80 mg/m ²/day + oxaliplatin 40 mg/m ²), with concurrent radiotherapy at daily fractions of 1.8 Gy 5 days per week, to a total dose of 41.4 Gy. Surgical resection, including D2 dissection, was performed within 4 weeks after the last day of chemotherapy. Results Chemoradiotherapy was generally well tolerated, with the most common dose-related grade 1 or 2 adverse events being anemia, nausea, vomiting, anorexia and abdominal pain. Two DLTs (prolonged thrombocytopenia and stomach perforation) were observed at dose level 1 (n = 6) and resulted in dose de-escalation to level -1. The recommended dose for future study is dose level -1, at which 1 of 6 patients developed grade 3 vomiting and anorexia. R0 resection was possible in 11 patients. Pathologic down-staging was observed in 6 patients, including one complete response. No clinically relevant postoperative complications occurred. Conclusions The activity of preoperative concurrent chemoradiotherapy with S-1 (60 mg/m ²/day for 28 consecutive days) and oxaliplatin (40 mg/m ² on days 1, 8, 15 and 22) will be explored more extensively in a phase II study in patients with locally advanced GC.