Neoadjuvant docetaxel, oxaliplatin and S-1 therapy for the patients with large type 3 or type 4 gastric cancer (OGSG1902): protocol of a multi-center, phase II study

BACKGROUND: Large type 3 and type 4 gastric cancers have extremely poor prognoses. To address this, neoadjuvant chemotherapy may be a promising approach. The phase III JCOG0501 study, conducted to confirm the superiority of neoadjuvant S-1 plus cisplatin followed by D2 gastrectomy over upfront surgery, showed no survival benefit for neoadjuvant S-1 plus cisplatin. In Korea, the PRODIGY study, which was a phase III study of neoadjuvant docetaxel plus oxaliplatin plus S-1 (DOS) followed by surgery and adjuvant S-1 versus surgery and adjuvant S-1 for gastric cancer of T2-3N+ or T4Nany, showed that progression-free survival (PFS) was significantly superior in the neoadjuvant DOS arm. Therefore, DOS therapy may be a promising candidate for preoperative chemotherapy for large type 3 or type 4 gastric cancer. METHODS: Preoperative docetaxel 40 mg/m(2) and oxaliplatin 100 mg/m(2) will be intravenously administered on day1 every three weeks. S-1 will be orally administered 80 mg/m(2) on days 1–14 of a 21-day cycle. Patients will receive three courses of treatment and gastrectomy with ≥D2 lymph node dissection. Postoperative S-1 plus docetaxel therapy (DS) will be administered according to the JACCRO GC-07 (START-2) study. The primary endpoint is the 3-year PFS rate. Secondary endpoints include PFS time, overall survival time, pathological response rate, response rate according to RECIST version1.1, proportion of completion of neoadjuvant chemotherapy, R0 resection rate, proportion of completion of surgery, proportion of completion of protocol treatment, proportion of negative conversion of CY, adverse event occurrence rate, and nutritional evaluation. The null hypothesis for the 3-year PFS rate is 45% and the expected value is 60%. The total sample size is 46 considering that the registration period and follow-up period are two and three years, respectively. DISCUSSION: This is a prospective, multicenter, single-arm, open-label, phase II trial assessing the efficacy and safety of preoperative DOS and postoperative DS for large type 3 or type 4 gastric cancer. The results will inform future phase III trials and are expected to lead to new treatment strategies for large type 3 or type 4 gastric cancer. TRIAL REGISTRATION: Registered with Japan Registry of Clinical Trials on October 11, 2019 (jRCTs051190060).