Vaccine Therapy Plus QS21 in Treating Patients With Advanced Pancreatic or Colorectal Cancer

DISEASE CHARACTERISTICS: Histologically confirmed advanced pancreatic or colorectal adenocarcinoma Curatively unresectable OR Recurrent following potentially curable resection OR Pancreatic adenocarcinoma that has been surgically resected within the past 12 months Must have one of the following ras gene mutations at codon 12: Glycine to cysteine Glycine to aspartic acid Glycine to valine HLA A2 required if evidence of HLA restriction for peptide presentation PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 3 months Hematopoietic: WBC at least 3,500/mm3 Lymphocyte count at least 500/mm3 Hepatic: Bilirubin no greater than 3 mg/dL Renal: Creatinine no greater than 2 times upper limit of normal OR Creatinine clearance at least 50 mL/min Other: No active infection requiring sytemic therapy No history of severe allergy or anaphylaxis No immunodeficiency (e.g., HIV infection, lupus, or myeloma) Not pregnant Negative pregnancy test Fertile patients must use effective contraception Women must use contraception for 3 months prior to, during and for 3 months after study Men must use contraception during and for 3 months after study PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior immunologic therapy No other concurrent systemic immunotherapy for cancer Chemotherapy: At least 4 weeks since prior chemotherapy No concurrent systemic chemotherapy for cancer Endocrine therapy: At least 4 weeks since prior corticosteroids No concurrent corticosteroids Radiotherapy: At least 4 weeks since prior radiotherapy Surgery: See Disease Characteristics Other: At least 4 weeks since prior immunosuppressants (e.g., methotrexate) No concurrent immunosuppressants Concurrent nonsteroidal antiinflammatory drugs for pain palliation allowed