PRIOR CONCURRENT THERAPY: Biologic therapy: No prior immunotherapy, vaccine therapy, cytokine therapy, or biologic therapy for metastatic disease No prior angiogenesis inhibition therapy (e.g., metalloproteinase inhibitors, thalidomide, anti-VEGF/Flk-1 monoclonal antibody therapy or other experimental drugs acting directly on the VEGF/Flk-1 signaling pathway) Prior antibody therapy, immunotherapy, gene therapy, vaccine therapy, cytokine therapy, or radioimmunotherapy allowed in adjuvant setting only Concurrent epoetin alfa, filgrastim (G-CSF), or sargramostim (GM-CSF) allowed for anemia, neutropenia, or thrombocytopenia No concurrent immunotherapy Chemotherapy: No prior systemic chemotherapy for metastatic disease No prior intra-arterial cytotoxic chemotherapy No more than one prior course of fluorouracil based adjuvant therapy (e.g., intravenous fluorouracil or capecitabine) with the last dose administered at least 6 months ago No prior SU5416 No other concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: At least 2 weeks since prior radiotherapy Concurrent localized palliative radiotherapy allowed unless indicative of disease progression Surgery: At least 4 weeks since prior major surgery (not including surgical placement of a venous access device) Prior surgical resection of hepatic metastases allowed Other: No prior investigational therapy for metastatic disease No other concurrent investigational agents