Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed adenocarcinoma of the breast, meeting criteria for 1 of the
following:

- Metastatic disease currently in complete or partial response or stable disease

- Have been receiving a stable endocrine therapy regimen (e.g., aromatase
inhibitor, tamoxifen, fulvestrant, or gonadotropin-releasing hormone
agonist) for at least 30 days OR status post oophorectomy

- Completed a course of local and adjuvant systemic therapy for high-risk stage II
or III disease (i.e., anticipated 5-year relative survival is no greater than
50%) meeting any of the following staging criteria:

- Stage IIB with involvement of at least 4 nodes

- Stage IIIA (T3 disease with involvement of at least 4 nodes)

- Any stage IIIB or IIIC disease

- Stage IV with no evidence of disease (e.g., prior resection of local chest wall
recurrence with no evidence of disease elsewhere)

- 1+, 2+, or 3+ HER2/neu expression by immunohistochemistry

- Treatment with trastuzumab (Herceptin®) not clinically indicated

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

Age

- 18 and over

Sex

- Female

Menopausal status

- Not specified

Performance status

- ECOG 0-1

Life expectancy

- At least 6 months

Hematopoietic

- Platelet count at least 100,000/mm^3

- Hemoglobin at least 10 g/dL

- Absolute neutrophil count at least 1,500/mm^3

Hepatic

- ALT or AST no greater than 2.5 times upper limit of normal (ULN) (5 times ULN for
patients with liver metastases)

- Bilirubin no greater than 2 mg/dL (unless due to Gilbert's disease)

Renal

- Creatinine no greater than 2 mg/dL

Cardiovascular

- No history of significant cardiovascular disease

- No myocardial infarction within the past 6 months

- No poorly controlled cardiac arrhythmia

- No New York Heart Association class III or IV heart disease

- LVEF at least 50% by MUGA

Other

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No other malignancy except basal cell skin cancer or adequately treated carcinoma in
situ of the cervix

- No concurrent severe autoimmune disease

- No other clinically significant or serious medical disease that would preclude study
participation or compromise patient safety or the results of this study

PRIOR CONCURRENT THERAPY:

Biologic therapy

- More than 4 months since prior trastuzumab

- No prior anticancer vaccine therapy

- No concurrent trastuzumab

- No concurrent immunomodulators (e.g., thalidomide or interferons/interleukins)

Chemotherapy

- More than 4 weeks since prior chemotherapy

- No concurrent low-dose methotrexate or cyclophosphamide

- No concurrent cytotoxic chemotherapy

Endocrine therapy

- See Disease Characteristics

- No concurrent corticosteroids

- Topical or inhaled steroids are allowed

- No changes to current endocrine therapy regimen (e.g., discontinuation or addition of
an agent)

Radiotherapy

- More than 3 months since prior radiotherapy involving more than 25% of the bone
marrow

- No concurrent radiotherapy

Surgery

- See Disease Characteristics

- No prior bilateral breast procedures

Other

- More than 4 weeks since prior immunosuppressive therapy

- More than 30 days since prior investigational agents or clinical trial participation

- No other concurrent experimental or investigational agents

- No concurrent cyclosporine

- No concurrent immunosuppressive agents