HER2 ICD peptide-based vaccine(University of Washington)

This randomized phase I/II trial studies the side effects of vaccine therapy with or without polysaccharide-K and to see how well it works in treating patients with stage IV human epidermal growth factor receptor 2 (HER2) positive breast cancer who are receiving HER2-targeted monoclonal antibody therapy. Vaccines made from HER2 intracellular domain (ICD) peptide may help the body build an effective immune response to kill tumor cells that express HER2. Polysaccharide-K may stimulate the immune system in different ways and stop tumor cells from growing. It is not yet known whether vaccine therapy works better when given with or without polysaccharide-K in treating breast cancer.