A Phase I Trial of Oxaliplatin, Irinotecan, and S-1 Combination Therapy (OX-IRIS) as Chemotherapy for Unresectable Pancreatic Cancer (HGCSG 1403).

Lessons learned Because S-1 is orally administered, OX-IRIS does not necessitate the continuous infusion of 5-FU and is more convenient. The recommended dose of OX-IRIS was determined to be level -1 (oxaliplatin, 65 mg/m2 ; irinotecan, 100 mg/m2 ; S-1, 80 mg/m2 ), which has manageable safety and promising anticancer activities. Background OX-IRIS is a new combination therapy of oxaliplatin, irinotecan, and S-1 for unresectable pancreatic ductal adenocarcinoma (PDAC), which may be beneficial because S-1 is administered orally and continuous infusion of 5-fluorouracil (5-FU) is not needed. Methods Patients who had not received prior therapy for unresectable PDAC were enrolled. Adenocarcinoma or adenosquamous histology was required. Oxaliplatin and irinotecan were administered on days 1 and 15; S-1 was administered orally twice a day on days 1-14, followed by 14 days of rest (one cycle). Primary endpoints were dose-limiting toxicity (DLT) and maximum tolerated dose (MTD). Secondary endpoints were safety, overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). Results In level 0 (oxaliplatin, 85 mg/m2 ; irinotecan, 100 mg/m2 ; S-1, 80 mg/m2 ), two of five patients experienced DLT. In level -1 (oxaliplatin, 65 mg/m2 ; irinotecan, 100 mg/m2 ; S-1, 80 mg/m2 ), DLT could not be evaluated in two of eight patients because one cycle was not completed; one of the remaining six patients experienced DLT. Anemia, thrombocytopenia, fatigue, nausea, anorexia, diarrhea, and peripheral sensory neuropathy were seen frequently in levels 0 and -1. ORR was 30% in levels 0 and -1. Median progression-free survival and median overall survival were 4.1 months (95% confidence interval [CI], 0.0-8.9 months) and 13.7 months (95% CI, 4.8-22.6 months), respectively. Conclusion MTD of OX-IRIS therapy was estimated to be level 0, and the recommended dose (RD) for future trial was level -1.