DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed adenocarcinoma of the breast

  • Locally advanced or metastatic disease

• Metastatic disease must be measurable or evaluable

  • Patients with bone only metastases are eligible provided there is an evaluable site of bone metastasis that can be followed by x-ray, MRI, or CT scan

• Relapsed or progressed during prior treatment with single-agent nonsteroidal aromatase inhibitor (NSAI)*, meeting either of the following criteria:

  • NSAI given as adjuvant therapy that lasted ≥ 12 months

  • Achieved an objective complete response, partial response, or stable disease that lasted ≥ 6 months after prior first-line therapy with NSAI for locally advanced or metastatic disease

    • Chemotherapy as part of the first-line therapy given before initiation of NSAI allowed NOTE: *Patients are required to continue to take NSAI until beginning of study treatment.
• No rapidly progressive visceral disease (i.e., lymphangitis carcinomatosa or diffuse hepatic involvement)

• Hormone receptor status:

  • Estrogen receptor (ER) and/or progesterone receptor positive tumor
  • No ER-unknown disease

PATIENT CHARACTERISTICS:

Sex

• Female

Menopausal status

• Postmenopausal, as defined by 1 of the following criteria:

  • Age 60 and over
  • Age 45 to 59 AND ≥ 12 months since last menstrual period with no prior hysterectomy
  • Any age with prior bilateral oophorectomy

Performance status

• WHO 0-2

Life expectancy

• More than 3 months

Hematopoietic

• Neutrophil count ≥ 1,500/mm^3

• Platelet count ≥ 100,000/mm^3

  • No thrombocytopenia
• Hemoglobin ≥ 10 g/dL

Hepatic

• AST and ALT ≤ 2.5 times upper limit of normal (ULN)
• Alkaline phosphatase ≤ 5 times ULN (unless due to bone metastases)
• No liver disease

Renal

• Creatinine < 1.97 mg/dL

Other

• No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

Chemotherapy

• See Disease Characteristics
• Prior neoadjuvant or adjuvant chemotherapy allowed

Endocrine therapy

• See Disease Characteristics
• Prior tamoxifen as neoadjuvant or adjuvant therapy allowed
• No systemic corticosteroids that lasted > 15 days within the past 4 weeks

Other

• More than 4 weeks since prior investigational drugs

• Concurrent bisphosphonates for bone metastases allowed provided bisphosphonate therapy has been established for ≥ 6 months

  • Concurrent initiation of bisphosphonate allowed provided patient has soft tissue or visceral metastases as the measurable or evaluable target lesion
• No concurrent anticoagulant therapy
• No concurrent unlicensed noncancer investigational agents