A phase II study of biweekly oxaliplatin plus S-1 combination chemotherapy as a first-line treatment for patients with metastatic or advanced gastric cancer in China

Oxaliplatin plus S-1 (SOX) was a first-line regimen for advanced gastric cancer. The continuous administration of S-1 for 3 weeks can result in unacceptable gastrointestinal and hematological toxicities. Therefore, an alternative regimen (administration of S-1 for 1-week followed by 1-week rest) is warrant for improved tolerability and noninferiority efficacy. We conducted a study to evaluate the efficacy and safety of biweekly SOX as the first-line chemotherapy in patients with metastatic or advanced gastric cancer in China. Patients with metastatic or previously untreated advanced gastric cancer were enrolled. Oxaliplatin was administered intravenously at a dose of 85 mg/m(2) on day 1, while S-1 was administered orally in doses of 80, 100, or 120 mg/day depending on different body surface areas of <1.25 m(2), 1.25–1.5 m(2), or >1.5 m(2) respectively; the total dose of S-1 was administered twice daily on days 1–7 followed by a 7-day rest. This schedule was repeated every 2 weeks until disease progressed or intolerable toxicity occurred. Forty-six patients (M/F = 33/13) received biweekly oxaliplatin and S-1 as first-line chemotherapy. A total of 257 treatment cycles were administered and the median number of cycles administered was 6. Thirty-six patients (78.3%) received second-line chemotherapy. The median progression free survival and median overall survival was 4.4 months (95% CI, 3.37–5.36 months) and 10.3 months (95% CI, 8.88–11.3 months), respectively. The 1-year and 2-year survival rate was 41% and 13%. The objective response rate was 30.43%, and the disease control rate was 76.08%. The observed adverse events of Grade 3/4 included were leukocytopenia (13.04%); anemia (13.04%); neutropenia (15.22%); neurological toxicity (2.17%); diarrhea (2.17%). The biweekly SOX regimen as first-line treatment was active and well tolerated in Chinese patients with metastatic or advanced gastric cancer.