DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed adenocarcinoma of the breast at first diagnosis

  • Stage IV disease
• Measurable disease

• HER2/neu-positive disease by fluorescence in situ hybridization

  • Amplification ≥ 2.0
• No prior or current brain metastases

• Hormone receptor status:

  • Estrogen receptor- and/or progesterone receptor-positive tumor by immunohistochemistry

    • At least 10% tumor staining OR Allred score ≥ 3 for positivity

PATIENT CHARACTERISTICS:

Age

• Postmenopausal

Sex

• Female

Menopausal status

• Postmenopausal, defined by 1 of the following:

  • Prior bilateral oophorectomy
  • 60 years of age or older
  • 45 years of age or older with amenorrhea for ≥ 12 months AND uterus is intact
  • Follicle-stimulating hormone and estradiol levels within postmenopausal range

Performance status

• ECOG 0-2

Life expectancy

• At least 24 weeks

Hematopoietic

• Absolute neutrophil count ≥ 1,000/mm^3
• Hemoglobin ≥ 10 g/dL
• Platelet count ≥ 100,000/mm^3
• No history of bleeding diathesis (e.g., disseminated intravascular coagulation or clotting factor deficiency)

Hepatic

• Bilirubin ≤ 1.5 times upper limit of normal (ULN) (Gilbert's syndrome allowed)
• AST and ALT ≤ 2.5 times ULN
• Alkaline phosphatase ≤ 5.0 times ULN, except in the presence of documented bone metastases and the absence of known hepatic disease

Renal

• Creatinine ≤ 2.0 mg/dL

Cardiovascular

• LVEF ≥ lower limit of normal
• No New York Heart Association class II-IV congestive heart failure
• No uncontrolled hypertension
• No myocardial infarction
• No unstable angina
• No serious cardiac arrhythmia requiring medication
• No other clinically significant cardiovascular disease

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for ≥ 3 months after completion of study treatment
• No other malignancy within the past 5 years except nonmelanoma skin cancer or carcinoma in situ of the cervix
• No active uncontrolled infection requiring parenteral antimicrobials
• No other medical or psychiatric disorder that would preclude study treatment
• No known hypersensitivity to any of the study drugs or to active or inactive excipients of fulvestrant (e.g., castor oil or mannitol)

PRIOR CONCURRENT THERAPY:

Biologic therapy

• At least 6 months since prior adjuvant trastuzumab (Herceptin®)
• No prior trastuzumab for metastatic breast cancer

Chemotherapy

• Prior adjuvant chemotherapy allowed
• No prior chemotherapy for metastatic breast cancer
• No concurrent chemotherapy

Endocrine therapy

• At least 6 months since prior adjuvant tamoxifen or aromatase inhibitor therapy
• At least 4 weeks since prior endocrine therapy (4 months for luteinizing hormone-releasing hormone analog) and recovered
• No prior fulvestrant
• No prior endocrine therapy for metastatic breast cancer
• No other concurrent endocrine therapy

Radiotherapy

• At least 4 weeks since prior radiotherapy and recovered
• No concurrent radiotherapy

Surgery

• At least 4 weeks since prior surgery and recovered

Other

• No prior investigational therapy for metastatic breast cancer
• No other concurrent investigational agents
• No other concurrent anticancer therapy

• No concurrent long-term anticoagulant therapy, except antiplatelet therapy (e.g., warfarin)

  • Concurrent low-dose warfarin allowed provided INR is ≤1.6