Phase II study of adjuvant chemotherapy of S-1 plus oxaliplatin for patients with stage III gastric cancer after D2 gastrectomy

Background: The Adjuvant Chemotherapy Trial of S-1 for Gastric Cancer (ACTS-GC) demonstrated a survival benefit by adjuvant S-1 monotherapy in patients who had undergone curative resection of stage II/III gastric cancer, but there is still a need to improve the efficacy of treatment of stage III disease. We investigated the tolerability and safety of S-1 and oxaliplatin as adjuvant chemotherapy for stage III gastric cancer. Methods: Japanese patients with stage III gastric cancer who had undergone D2 or more extensive lymphadenectomy were enrolled. In the first cycle, S-1 (40–60 mg/m² twice daily) alone was given orally for 2 weeks of a 3-week cycle. From the second cycle, S-1 was administered as in the first cycle and oxaliplatin (100 mg/m²) was infused intravenously on day 1. Treatment was continued for 8 cycles. The primary end point was the treatment completion rate for eight cycles. Results: Sixty-three patients were enrolled and 62 patients were included in analysis. The treatment completion rate was 74.2 %, which was higher than the expected completion rate of 72.0 %. The median relative dose intensities were 77.1 % for S-1 and 72.6 % for oxaliplatin, with 41.9 and 61.7 % patients requiring dose reduction of S-1 and oxaliplatin, respectively. Neutropenia was the only grade 3 or higher adverse event with an incidence 10 % or greater (32.3 %). There was no grade 3 or higher peripheral sensory neuropathy or treatment-related death. Conclusions: S-1 and oxaliplatin therapy is suggested to be manageable and safe with optimal dose reduction and delay in selected patients for stage III gastric cancer after D2 gastrectomy, and warrants further evaluation in larger studies.