ARM E (closed to accrual as of 6/1/2005--currently enrolled patients may cross over to arm D for remainder of therapy): Patients receive cetuximab* as in arm D and irinotecan hydrochloride, leucovorin calcium, and fluorouracil as in arm B. Treatment repeats every 14 days for up to 12 courses in the absence of unacceptable toxicity or recurrent disease.