RATIONALE: Vaccines may make the body build an immune response to tumor cells. Colony-stimulating factors such as sargramostim increase the number of immune cells found in bone marrow or peripheral blood.

PURPOSE: Phase I trial to study the effectiveness of vaccine therapy plus sargramostim in treating patients who have stage III or stage IV cancer.

OBJECTIVES: I. Determine the safety of serial intradermal or subcutaneous vaccinations of HER-2 derived p369-377 peptide incorporated into polylactide-co-glycolide (PLG) microspheres with adjuvant sargramostim (GM-CSF) in patients with stage III or IV HER-2 expressing cancers. II. Determine whether cytotoxic T lymphocytes (CTL) specific for the HER-2 protein can be elicited in patients with HLA-A2 by immunization with this regimen. III. Determine which route of immunization, intradermal or subcutaneous, is more effective in generating HER-2 specific CTL in these patients on this regimen. IV. Determine the extent to which escalated dose of PLG peptide affects the immune response in these patients on this regimen.

OUTLINE: Patients undergo leukapheresis prior to study and after final vaccination. Patients are sequentially entered into one of three treatment arms: Arm I: Patients receive an intradermal vaccination of HER-2 derived p369-377 peptide incorporated into polylactide-co-glycolide (PLG) microspheres with adjuvant sargramostim (GM-CSF). Arm II: Patients receive a subcutaneous vaccination of HER-2 derived p369-377 peptide incorporated into PLG microspheres with adjuvant GM-CSF. Arm III: Patients receive a higher dose of subcutaneous vaccination of HER-2 derived p369-377 peptide incorporated into PLG microspheres with adjuvant GM-CSF. Treatment repeats every 4 weeks for up to 6 courses in the absence of unacceptable toxicity.

PROJECTED ACCRUAL: A total of 15 patients (5 per treatment arm) will be accrued for this study.

DISEASE CHARACTERISTICS: Stage III adenocarcinoma that overexpresses HER-2 and previously treated by surgical resection, conventional chemotherapy, or radiotherapy OR Stage IV adenocarcinoma that overexpresses HER-2 and in stable or complete remission with no other concurrent chemotherapy Must have documented HER-2 protein overexpression in the primary or metastatic tumor HLA-A2 positive

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 90-100% Life expectancy: At least 12 months Hematopoietic: WBC greater than 3,500/mm3 Platelet count greater than 100,000/mm3 Hepatic: Bilirubin less than 1.5 mg/dL Renal: Creatinine less than 1.5 mg/dL OR Creatinine clearance greater than 60 mL/min Other: Female patients must have completed childbearing Fertile male patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics At least 4 weeks since prior cytotoxic chemotherapy Endocrine therapy: At least 4 weeks since prior corticosteroids Radiotherapy: See Disease Characteristics Surgery: See Disease Characteristics Other: No other concurrent investigational phase I studies