Background: FOLFIRINOX is considered one of the standard chemotherapy regimens for chemotherapy-naïve pts. with MPC, but carries an unfavorable adverse event (AE) profile, especially in Japanese Phase II study of full dose FOLFIRINOX, the incidence of grade 3 or more neutropenia and febrile neutropenia was 77.8% and 22.2% respectively. Objective: The purpose of this study was to evaluate the efficacy and safety of modified FOLFIRINOX regimen: intravenous oxaliplatin 85 mg/m², irinotecan 150 mg/m², 5-FU infusion 2,400 mg/m²over 46 h, no bolus 5-FU. Methods: This study was an open-label, multicenter, single-arm phase II study. The primary endpoint was overall survival and the incidence of grade 3 or more neutropenia. All patients did not receive prophylactic pegfilgrastim. Results: Sixty-nine pts. were enrolled from 39 institutions in Japan. Median age was 62.6 years (range 42.4 - 74.2). All pts. had no prior treatment and had distant metastatic lesions. 68.1% of the pts. had a PS 0, the primary site of the tumor was the head of the pancreas in 44.9% of pts., 20.3% of pts. had a biliary stent, and 5.8% of pts. experienced recurrence after resection. The UGT1A1 genotype was wild type in 79.7%, heterozygous (*1/*6, *1/*28) in 20.3%. Median overall survival was 11.2 months (95% confidence interval [CI], 9.0-) and the 1-year survival proportion was 0.481. Median progression-free survival was 5.5 months (95% CI, 4.1-6.7). The response rate was 37.7% (95% CI, 26.3-50.2) and disease control rate was 78.3% (95% CI, 66.7–87.3). The incidence of grade 3 or more neutropenia was 47.8%. Other major grade 3 or more toxicities were febrile neutropenia (8.7%), thrombocytopenia (2.9%), anemia (4.3%), anorexia (15.9%), diarrhea (10.1%), nausea (8.7%), cholangitis (5.8%) and peripheral sensory neuropathy (5.8%). Serious adverse events occurred in 6 pts. (8.7%). All AE proportions were less than those in the previous Japanese full dose Phase II study. One patient died due to interstitial pneumonia related to a treatment. Conclusions: This is the first prospective study of modified FOLFIRINOX in Asia. Modified FOLFIRINOX of this study has an improved safety profile with maintained efficacy in MPC without prophylactic pegfilgrastim. Clinical trial information: UMIN000013301.