Background: In a randomized pivotal global phase III study, S-1 and oxaliplatin 100 mg/m2 (SOX100) combination chemotherapy was as effective as S-1 and cisplatin for advanced gastric cancer (AGC) and showed a favorable safety profile. In this phase II study, we analyzed survival outcomes to assess the efficacy and safety of the SOX regimen with oxaliplatin 130 mg/m2 (SOX130) in AGC. Methods: Patients with HER2-negative AGC received 80 mg/m2/day S-1 orally on days 1–14 and 130 mg/m2 oxaliplatin intravenously on day 1 of each 21-day cycle until the criteria for treatment withdrawal were fulfilled. The primary endpoint was the response rate (RR), and the null hypothesis of RR in the current trial was 45%. The secondary endpoints were progression-free survival (PFS) and overall survival (OS). Adverse events (AEs) were recorded according to CTCAE version 4.0. Results: Seventy-one patients were enrolled from June 2015 to November 2016, but eight were excluded for ineligibility. Therefore, all final analyses were conducted with 63 patients. The confirmed RR was 46.0% (90% confidence interval [CI]: 36.1–56.3), and the disease control rate was 77.8% (90% CI: 68.1–85.1). The median PFS and OS were 4.9 (95% CI: 4.2–7.1) and 14.8 (95% CI: 11.1–18.9) months, respectively. Incidences of grade 3–4 AEs > 10% were anorexia (19.0%), peripheral neuropathy (12.7%), nausea (11.1%), and thrombocytopenia (11.1%). Conclusions: This study represents the first evaluation of SOX130 in patients with HER2-negative AGC. SOX130 showed an acceptable safety profile, but the prespecified statistical efficacy targets were not achieved.
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