Phase II study of neoadjuvant chemotherapy with S-1 plus oxaliplatin for gastric cancer clinical T4 or N2-3

In Japan, the standard treatment for stage II or III gastric cancer is D2 gastrectomy followed by administration of S-1 for one year. However, patients with stage III disease have unsatisfactory survival rates. The purpose of this study was to evaluate the efficacy and safety of neoadjuvant chemotherapy consisting of S-1 and oxaliplatin for advanced gastric cancer. Patients with cT4 or cN2–3 gastric cancer were scheduled to receive two courses of chemotherapy (130 mg/m² oxaliplatin on Day 1, 80 mg/m² S-1 per day twice daily for 14 days) followed by surgery. The primary endpoint was the R0 resection rate. The secondary endpoints were rates of completion of protocol treatment, pathological response, and adverse events; and 3-year overall survival, 5-year overall survival, and 5-year recurrence-free survival. Between May 2016 and March 2019, 30 patients were enrolled in the study, all of whom completed the protocol treatment. The R0 resection rate (primary endpoint) was 93.3% (95% confidence interval: 77.9–99.2). The pathological response rate was 63.3%. Grade 3–4 toxicities included anemia (3.3%), anorexia (6.7%), and fatigue (3.3%). Relative dose intensities were 91.2% and 94.2% for S-1 and oxaliplatin, respectively. Neoadjuvant S-1 and oxaliplatin is highly effective, achieving an acceptable R0 resection rate with relatively few severe toxicities and good compliance. Trial registration: Registry name: A prospective intervention study on the availability of preoperative SOX therapy for T4 or N2-3 gastric cancer. Trial ID: UMIN: UMIN000024656. https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R00002836.