Background: Although FOLFIRINOX is superior to gemcitabine in MPC, the regimen is associated with significant toxicities (Conroy et al. N Engl J Med 2011;364:1817). In our prior retrospective analysis, efficacy was not compromised by dose attenuations of FOLFIRINOX (Gunturu et al. Med Oncol 2013;30:361). Based on this analysis, a prospective phase II open label study to evaluate the efficacy and tolerability of mFOLFIRINOX in pts with locally advanced (LAPC) and MPC was conducted. Herein, we report the final analysis of the toxicity in LAPC and MPC, and the efficacy in MPC. Methods: Previously untreated pts with MPC or LAPC received mFOLFIRINOX every two wks with 25% dose reductions of irinotecan & bolus 5FU until progression, unacceptable toxicity, or surgical resection. All pts received prophylactic pegfilgrastim. CAT scans were obtained every 4 cycles for response assessment by RECIST. Toxicities in the entire cohort, and response rate (RR) & pt characteristics in the MPC cohort were compared to historical data reported by Conroy. PFS was determined for MPC cohort. Results: 31 pts with LAPC and 43 pts with MPC with ECOG PS 0/1 were enrolled between 11/11 and 01/14. Characteristics of evaluable (37/43) MPC pts were: med age, 61 yrs (range 50-76); male, 21; ECOG PS 0, 17; med # metastatic sites, 2; peritoneal disease, 14; biliary stent, 9; med # of cycles 10 (range 4-31). Grade 3/4 toxicities in entire cohort were: vomiting & peripheral neuropathy, 2.7%; ALT elevated, thromboembolism and febrile neutropenia, 4.1%; anemia, 5.4%; diarrhea,16.2% (no grade 4 diarrhea reported); neutropenia & fatigue, 12.2%; thrombocytopenia, 9.5%. Neutropenia (p<0.0001), vomiting (p=0.0014), and fatigue (0.0194) were significantly decreased compared to historical data. RR in 37 pts with MPC was 35.1% (0 CR, 13 PR, 19 SD, 5 PD) and similar to historical data (36.9%; p 0.86). PFS in MPC pts was 6.11 mo with 95% CI (5.29, 8.31). Conclusions: mFOLFIRINOX with prophylactic pegfilgrastim in pts with MPC is associated with improved tolerability compared to full dose FOLFIRINOX, while RR and PFS in pts with MPC is similar to that reported by Conroy et all using full dose FOLFIRINOX. MPC pts are in follow-up for OS. Follow up for LAPC patients is ongoing. Clinical trial information: NCT01523457