Patients receive cetuximab IV over 1-2 hours on days 1, 8, 15, 22, and 29, oxaliplatin IV over 2 hours on days 1 and 15, irinotecan hydrochloride IV over 30 minutes on days 8 and 22, fluorouracil IV over 24 hours on days 1, 8, 15, and 22, leucovorin calcium IV on days 1, 8, 15, and 22, and bevacizumab IV over 30-90 minutes on days 1 and 15. Treatment repeats every 5 weeks for up to 3 courses in the absence of disease progression or unacceptable toxicity.