OUTLINE: Randomized study. The following acronyms are used: CF Leucovorin calcium, NSC-3590 5-FU Fluorouracil, NSC-19893 Arm I: Single-Agent Chemotherapy with Drug Modulation. 5-FU; with CF. Weekly infusion via an implantable pump. Arm II: Single-Agent Chemotherapy with Drug Modulation. 5-FU; with CF. Weekly infusion via a subcutaneous infusion port. Arm III: Single-Agent Chemotherapy with Drug Modulation. 5-FU; with CF. Monthly infusion via an implantable pump. Arm IV: Single-Agent Chemotherapy with Drug Modulation. 5-FU; with CF. Monthly infusion via a subcutaneous infusion port.