Combination Chemotherapy With or Without Celecoxib in Treating Patients With Metastatic Colorectal Cancer

RATIONALE: Drugs used in chemotherapy such as irinotecan, capecitabine, leucovorin, and fluorouracil use different ways to stop tumor cells from dividing so they stop growing or die. Celecoxib may stop the growth of colorectal cancer by stopping blood flow to the tumor. It is not yet known which combination chemotherapy regimen with or without celecoxib is more effective in treating metastatic colorectal cancer.
PURPOSE: This randomized phase III trial is studying two combination chemotherapy regimens and celecoxib to see how well they work compared to two combination chemotherapy regimens alone in treating patients with metastatic colorectal cancer.