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Background: FOLFOXIRI (fluorouracil, leucovorin, oxaliplatin, and irinotecan) plus bevacizumab has shown to be one of the therapeutic regimens in first line with the highest activity in patients (pts.) with metastatic colorectal cancer (mCRC) unselected for biomolecular alterations. Generally, tumors co-opt the programmed death-1/ligand 1 (PD-1/PD-L1) signaling pathway as one key mechanism to evade immune surveillance. As today, anti-PD-1 monoclonal antibodies are FDA approved only for DNA mismatch repair deficient/microsatellite instability-high (MMRd/MSI-H), which represent only about 5% among all mCRC. Nowadays, there are no data demonstrating anti PD-1 activity in proficient and stable disease (MMRp/MSS). A different target in mCRC is also the Vascular Endothelial Growth Factor A (VEGF-A), which acts on endothelial cells to stimulate angiogenesis. VEGF-A inhibition with bevacizumab has shown to increase the immune cell infiltration, providing a solid rationale for combining VEGF targeted agents with immune checkpoint inhibitors. Based on these evidences, we explore the combination of triplet chemotherapy (FOLFOXIRI) with bevacizumab and nivolumab in pts. with mCRC RAS/BRAF mutant regardless of microsatellite status.Methods/design: This is a prospective, open-label, multicentric phase II trial where pts. with mCRC RAS/BRAF mutated, in first line will receive nivolumab in combination with FOLFOXIRI/bevacizumab every 2 weeks for 8 cycles followed by maintenance with bevacizumab plus nivolumab every 2 weeks. Bevacizumab will be administered intravenously at dose of 5 mg/kg every 2 weeks and nivolumab intravenously as a flat dose of 240 mg every 2 weeks. The primary endpoint is the overall response rate (ORR). This study hypothesis is that the treatment is able to improve the ORR from 66 to 80%. Secondary endpoints include OS, safety, time to progression, duration of response. Collateral translational studies evaluate the i) tumor mutational burden, and ii) genetic alterations by circulating free DNA (cfDNA) obtained from plasma samples. The trial is open to enrollment, 9 of planned 70 pts. have been enrolled.Trial Registration: NIVACOR is registered at ClinicalTrials.gov: NCT04072198 , August 28, 2019. [ABSTRACT FROM AUTHOR]