Combination Chemotherapy in Treating Patients With Colorectal Cancer

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Giving drugs at the time of day that allows for the best drug response may allow the doctor to give higher doses of chemotherapy drugs and kill more tumor cells.
PURPOSE: Randomized phase II trial to determine the best time to give irinotecan combined with fluorouracil, leucovorin, and oxaliplatin in treating patients who have colorectal cancer.