OBJECTIVES: I. Compare the survival and quality of life of patients with metastatic or recurrent colorectal cancer receiving palliative therapy with leucovorin/fluorouracil vs. continuous-infusion fluorouracil vs. ICI D1694. II. Compare the survival and quality of life of patients with stable or responding disease after 12 weeks of initial treatment randomized to receive 12 additional weeks of chemotherapy vs. no further treatment.

OUTLINE: This is a randomized study. Patients are stratified by participating institution. Patients are randomized to one of three treatment regimens. The first group receives leucovorin followed by fluorouracil every 14 days for a total of 6 courses. The second group receives continuous-infusion fluorouracil for 12 weeks. The third group receive ICI D1694 every 21 days for a total of 4 courses. Patients without progressive disease or excessive toxicity after 12 weeks of treatment are then randomized to receive continuing chemotherapy in 12 weekly cycles of their assigned chemotherapy or to proceed to observation with no further therapy, until evidence of disease progression. Patients are followed every 6 weeks.

PROJECTED ACCRUAL: A total of 900 patients will be entered.

DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the colon or rectum in one of the following categories: Locally advanced, metastatic, or recurrent disease suitable only for palliative chemotherapy Evaluable disease outside prior radiotherapy field Patients with disease confined to the liver are referred to protocol MRC-CR05

PATIENT CHARACTERISTICS: Age: Not specified Performance status: WHO 0-2 Life expectancy: Greater than 3 months Hematopoietic: WBC at least 4,000 ANC at least 2,000 Platelets at least 100,000 Hepatic: Not specified Renal: Creatinine no greater than 1.25 times normal OR Creatinine clearance greater than 65 mL/min Cardiovascular: No uncontrolled heart failure No uncontrolled angina Other: No uncontrolled medical illness (including infection) Able and willing to complete quality-of-life questionnaires No prior or concurrent malignancy likely to interfere with protocol treatment or evaluation

PRIOR CONCURRENT THERAPY: No prior systemic chemotherapy except fluorouracil-based adjuvant regimen (e.g., QUASAR) At least 6 months since chemotherapy