Comparison of Combination Chemotherapy Regimens in Treating Patients With Metastatic Colorectal Cancer

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Giving the drugs in different combinations may kill more tumor cells. PURPOSE: This randomized phase II trial is studying combination chemotherapy containing irinotecan and oxaliplatin to see how well it works compared to two standard combination chemotherapy regimens in treating patients with unresectable metastatic colorectal cancer.