OUTLINE: This is a randomized, multicenter study. Patients are stratified according to positive lymph node involvement (1-3 vs 4 or more), histology (high [poorly differentiated or undifferentiated] vs low [well to moderately differentiated]), and clinical T stage (T1 or T2 vs T3 vs T4). Patients are randomized to 1 of 6 treatment arms (as of 6/1/2005, patients are randomized to treatment arms I and IV only; arms II, III, V, and VI are closed to accrual). As of 8/18/2008, pre-screening for KRAS status was added with mutant KRAS (or KRAS not evaluable) patients put on arm G and wild-type KRAS patients randomized between arm A and arm D.