ARM A: Patients receive cetuximab IV over 1-2 hours on days 1, 8, 15, 22, 29, and 36; bevacizumab IV over 30-90 minutes on days 1*, 15, and 29 OR on days 1 and 22; and irinotecan IV over 30-90 minutes (at the same dose and schedule that the patient previously received) beginning on day 1.