Combination Chemotherapy as First-Line Therapy in Treating Older Patients With Metastatic Colorectal Cancer That Cannot Be Removed By Surgery

RATIONALE: Drugs used in chemotherapy, such as fluorouracil, leucovorin, and irinotecan, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving more than one drug (combination chemotherapy) in different doses or combinations may kill more tumor cells. It is not yet known which combination chemotherapy regimen is more effective in treating colorectal cancer.
PURPOSE: This randomized clinical trial is studying how well fluorouracil works together with leucovorin with or without irinotecan in treating older patients with metastatic colorectal cancer .