PRIOR CONCURRENT THERAPY: Biologic therapy: No prior immunotherapy for metastatic disease Chemotherapy: No prior chemotherapy for metastatic disease At least 6 months since prior adjuvant chemotherapy with no disease progression or after metastatic liver resection No prior chemotherapy with oxaliplatin or irinotecan Endocrine therapy: Not specified Radiotherapy: At least 2 weeks since prior radiotherapy Surgery: At least 2 weeks since surgery Other: At least 30 days since use of investigational agent