AbstractThe prognosis of pancreatic ductal carcinoma (PDAC) with peritoneal metastasis remains dismal. Systemic chemotherapy alone may not be effective, and the combination of intraperitoneal chemotherapy with systemic chemotherapy is expected to prolong the overall survival in patients with peritoneal metastasis. We have designed a randomized phase III trial to confirm the superiority of intravenous (i.v.) and intraperitoneal (i.p.) paclitaxel (PTX) with S-1 relative to gemcitabine plus nab-PTX (GnP), which is the current standard therapy for patients with metastatic PDAC. A total of 180 patients will be accrued from 30 institutions within 3 years. Patients will be randomly assigned in a 1:1 ratio to receive either i.v. and i.p. PTX with S-1 or GnP (target of 90 patients per group). The primary endpoint is overall survival; secondary endpoints are progression-free survival, response rate, proportion with negative peritoneal washing cytology during chemotherapy, proportion requiring conversion surgery, and adverse event profiles. Japan Registry of Clinical Trials jRCTs051180199 (https://jrct.niph.go.jp/).