DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed primary adenocarcinoma of the breast

  • Locally advanced or metastatic disease
• Not amenable to surgery or radiotherapy with curative intent

• At least 1 unidimensionally measurable lesion

  • At least 20 mm by conventional techniques OR 10 mm by CT scan
  • Not previously irradiated

• Meets 1 of the following criteria:

  • Previously treated with anthracycline and concurrent or sequential taxane therapy

    • Refractory to the most recent taxane-based chemotherapy, defined as 1 of the following:

      • Progressive disease during therapy or within 4 months of the last dose with or without documented response for advanced disease
      • Progressive disease within 6 months of completing taxane-based chemotherapy as neoadjuvant therapy
  • Resistant to prior chemotherapy, as defined by progressive disease within 6 months of completing prior chemotherapy for advanced disease
• No known brain metastases or carcinomatous meningitis* NOTE: *Baseline CT scan or MRI of the brain required if there is clinical suspicion of CNS metastases
• No spinal cord compression

• Hormone receptor status:

  • Not specified

PATIENT CHARACTERISTICS:

Age

• 18 and over

Sex

• Female

Menopausal status

• Not specified

Performance status

• ECOG 0-1

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 9.0 g/dL

Hepatic

• Bilirubin no greater than 1.5 times upper limit of normal (ULN)
• SGOT no greater than 2.5 times ULN (5 times ULN if liver involvement secondary to tumor is present)
• Albumin at least 3.0 g/dL

Renal

• Creatinine no greater than 1.5 mg/dL

Cardiovascular

• LVEF at least 50% or ULN by echocardiogram or MUGA

• None of the following within the past 6 months:

  • Myocardial infarction
  • Severe or unstable angina
  • Symptomatic congestive heart failure
  • Cerebrovascular accident or transient ischemic attack
  • Deep vein thrombosis or other significant thromboembolic event
• No ongoing cardiac dysrhythmias grade 2 or greater
• No atrial fibrillation of any grade

Pulmonary

• No pulmonary embolism within the past 6 months

Gastrointestinal

• No active inflammatory bowel disease
• No partial or complete bowel obstruction
• No chronic diarrhea

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No known HIV positivity
• No active infection
• 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
• No other severe acute or chronic medical or psychiatric condition or laboratory abnormality that would preclude study participation or confound study results

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No concurrent biological response modifiers
• No concurrent immunotherapy
• No concurrent sargramostim (GM-CSF)
• No other concurrent granulocyte colony-stimulating factors

Chemotherapy

• See Disease Characteristics
• Prior adjuvant chemotherapy allowed
• No prior topoisomerase I inhibitors
• No more than 2 prior chemotherapy regimens for advanced disease
• No prior high-dose chemotherapy that required hematopoietic stem cell rescue
• No other concurrent chemotherapy

Endocrine therapy

• Prior adjuvant hormonal therapy or hormonal therapy for advanced/metastatic disease allowed provided that therapy is discontinued before study entry
• No concurrent hormonal therapy

Radiotherapy

• See Disease Characteristics
• No prior radiotherapy to more than 25% of the bone marrow

• No concurrent radiotherapy during and for 5 days after study treatment

  • Palliative radiotherapy allowed provided no more than 20% of the bone marrow is involved

Surgery

• No coronary/peripheral artery bypass graft within the past 6 months

Other

• Recovered from prior therapy (except alopecia or neurotoxicity)
• At least 4 weeks since any other prior therapy
• More than 4 weeks since prior investigational agents
• No concurrent enrollment on another clinical trial
• No other concurrent approved or investigational anticancer treatment