Study protocol of the HGCSG1803: a phase II multicentre, non-randomised, single-arm, prospective trial of combination chemotherapy with oxaliplatin, irinotecan and S-1 (OX-IRIS) as first-line treatment for metastatic or relapsed pancreatic cancer.

INTRODUCTION: Combination chemotherapy with oxaliplatin, irinotecan, fluorouracil and leucovorin (FOLFIRINOX) has become one of the standard treatments for metastatic pancreatic cancer. However, the use of FOLFIRINOX requires prolonged infusion. Therefore, we planned to develop a new combination chemotherapy regimen with oxaliplatin, irinotecan and S-1 (OX-IRIS) for advanced pancreatic cancer. In the phase Ⅰ study that was conducted previously, the safety and recommended dose of OX-IRIS were assessed. In this study, we will evaluate the efficacy and safety of OX-IRIS. METHODS AND ANALYSIS: The HGCSG1803 study started as a multicentre, non-randomised, single-arm, prospective, phase II study in December 2019. Eligible subjects were patients with untreated metastatic or relapsed pancreatic cancer. OX-IRIS is administered as follows: 30 min infusion of antiemetic; 2-hour infusion of oxaliplatin (65 mg/m2); 1.5-hour infusion of irinotecan (100 mg/m2) on day 1 and 15 of each 4-week cycle; and oral S-1 (40 mg/m2) twice daily from after dinner on day one to after breakfast on day 15, followed by a 14-day rest, to be repeated every 2 weeks until disease progression, unacceptable toxicity or patient refusal. The primary endpoint is response rate. The secondary endpoints are overall and progression-free survival, safety and dose for each drug. Using a binomial test, a sample size of 40 patients was set with a threshold value of 10% and expected value of 30%. Registration of 40 cases is planned from 18 institutions in Japan. ETHICS AND DISSEMINATION: All the procedures will be conducted in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Declaration of Helsinki of 1964 and its later versions. All the patients will receive written information about the trial and will provide informed consent before enrolment. This trial was approved by the Hokkaido University Certified Review Board (approval No: 018-037). TRIAL REGISTRATION NUMBER: jRCTs011190008.