This single arm study will assess progression-free survival, feasibility of use and safety of Avastin in combination with 5-FU/FA, oxaliplatin and irinotecan (FOLFOXIRI) as first line treatment in patients with metastatic colorectal cancer. Patients will receive up to 12 bi-weekly cycles of Avastin (5mg/kg iv) in combination with this standard neoadjuvant chemotherapy regimen followed by up to 40 bi-weekly cycles with Avastin plus 5-FU/FA. The anticipated time on study treatment is until disease progression, and the target sample size is <100 individuals.