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