A phase II study of S-1 and oxaliplatin (SOx) combination chemotherapy as a first-line therapy for patients with advanced gastric cancer

Background Palliative chemotherapy has been shown to have a survival benefit for patients with recurrent or metastatic gastric cancer. 5-fluorouracil (5-FU) and cisplatin have been widely used in a variety of combinations. We conducted a phase II study of combination chemotherapy with new agents, S-1 and oxaliplatin (SOx), in advanced gastric cancer patients in an effort to evaluate the efficacy and toxicity of this regimen. Method Histologically confirmed recurrent or metastatic gastric cancer were treated by the oral administration of S-1 80 mg/m²/day on days 1–28, and oxaliplatin 85 mg/m² administered as a 90-min intravenous infusion on days 1, 15, and 29. Treatment courses were repeated every 6 weeks. Patients received a maximum of four cycles. Results From Feb 2006 to May 2008, 41 patients were enrolled in this study. The ratio of males to females was 28 to 13. The median patient age was 61 years (range, 36–74 years), and 85.4% (35/41) of the patients had a performance status (ECOG) of 1. The median number of chemotherapy cycles administered was 3 (range, 1–4). According to the results of our Intent-to-Treat analysis, 22 patients (53.7%) achieved a partial response (95% CI, 38–70%). 15 patients (36.6%) evidenced a stable disease, and 1 patient (2.4%) progressed during the course of the treatment. 3 patients were lost to follow-up prior to evaluation. The median time to progression and overall survival time were 4.6 months (95% CI, 3.4–5.8 months) and 7.8 months (95% CI, 6.9–8.7 months) from the start of the chemotherapy, respectively. A total of 114 cycles were assessed for toxicity. The major hematologic toxicities included grade 2 anemia (41.2%), grade 1-2 neutropenia (28.1%), and grade 1 thrombocytopenia (23.7%). Only 1 cycle of neutropenic fever occurred. The non-hematological toxicities observed were grade 3 vomiting (12.2%) and grade 3 diarrhea (4.9%). No treatment-related deaths occurred in our patient population during the study period. Conclusion The SOx regimen evidenced a relatively high response rate and was well tolerated as a first-line therapy for advanced gastric cancer.