ARM III (closed to accrual as of 4/20/2009): Patients receive single-agent irinotecan hydrochloride or FOLFIRI as outlined above and cetuximab as in arm I. Patients also receive a higher dose of bevacizumab (higher than in arm II) IV over 30 minutes on day 1. Courses repeat every 14-21 days (depending upon chemotherapy regimen) in the absence of disease progression or unacceptable toxicity.