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.