RATIONALE: Vaccines may help the body build an effective immune response to kill tumor cells. Giving vaccine therapy together with QS21 may cause a stronger immune response and kill more tumor cells.

PURPOSE: This clinical trial is studying the side effects and how well giving vaccine therapy together with QS21 works in treating patients with metastatic breast cancer.

OBJECTIVES:

Primary

• Determine the safety of sialyl Lewisª -keyhole limpet hemocyanin conjugate vaccine and QS21 immunoadjuvant in patients with metastatic breast cancer.
• Determine the IgG and IgM antibody response to this regimen in these patients.
• Determine the proportion of breast cancer cells expressing this antigen in these patients.

Secondary

• Monitor the presence of circulating tumor cells prior to, during, and after this regimen in these patients.

OUTLINE: Patients receive sialyl Lewisª -keyhole limpet hemocyanin conjugate vaccine subcutaneously (SC) and QS21 immunoadjuvant SC once in weeks 1, 2, 3, 7, and 19 in the absence of disease progression or unacceptable disease.

Blood samples are collected periodically and evaluated for circulating tumor cells and reactivity against sialyl Lewisª antigen in ELISA and/or immunoprecipitation-western blot assays.

After completion of study treatment, patients are followed every 3 months.

DISEASE CHARACTERISTICS:

• Histologically confirmed stage IV breast cancer meeting 1 of the following criteria:

  • No evidence of disease

  • Stable disease on hormonal therapy

    • Stable disease must be present for ≥ 2 months and include < 30% decrease or < 20% increase in the sum of the longest diameter of target lesion
    • No new target lesions or unequivocal progression of non-target lesions
    • Elevation in the CA 153 (BR2729) or CEA values allowed

• Hormone receptor status not specified

PATIENT CHARACTERISTICS:

• Female or male
• Menopausal status not specified
• Karnofsky performance status 80-100%
• Lymphocyte count ≥ 500/mm³
• WBC ≥ 3,000/mm³
• Creatinine ≤ 1.5 times upper limit of normal (ULN)
• AST ≤ 1.5 times ULN
• Alkaline phosphatase ≤ 1.5 times ULN
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No history of allergy to seafood
• No NYHA class III-IV cardiac disease
• No other active cancers except basal cell or squamous cell carcinoma of the skin
• No active infection requiring antibiotic treatment
• No known history of immunodeficiency or autoimmune disease

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 4 weeks since prior chemotherapy
• At least 4 weeks since prior radiotherapy
• At least 4 weeks since prior surgery
• At least 6 weeks since prior immunotherapy
• No prior sialyl Lewisª antigen
• No concurrent immunosuppressive medications (i.e., corticosteroids)
• Concurrent hormonal therapy allowed

2 years