DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed breast cancer

  • Clinical evidence of metastatic disease
• Measurable disease

• HER2-positive or -negative disease

  • If HER2 gene amplified or strongly positive for HER2 by immunohistochemistry, patient must have had prior treatment containing trastuzumab (Herceptin®) unless contraindicated
• Previously treated with anthracycline- and/or taxane-containing regimen in the neoadjuvant, adjuvant, or metastatic setting
• Candidate for first- or second-line chemotherapy for metastatic disease
• Core block or tumor slides of the primary or metastatic tumor available
• No known brain metastases

• Hormone receptor status:

  • Not specified

PATIENT CHARACTERISTICS:

Age

• 18 and over

Sex

• Male or female

Menopausal status

• Not specified

Performance status

• ECOG 0-1

Life expectancy

• At least 3 months

Hematopoietic

• WBC ≥ 3,000/mm^3
• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3
• Hemoglobin ≥ 8.5 g/dL
• No evidence of bleeding diathesis

Hepatic

• Bilirubin ≤ 1.5 times upper limit of normal (ULN)
• AST ≤ 3 times ULN
• Alkaline phosphatase ≤ 3 times ULN
• PT normal
• PTT normal
• INR normal

Renal

• Creatinine ≤ 1.5 times ULN
• Calcium normal

Cardiovascular

• No symptomatic congestive heart failure
• No unstable angina pectoris
• No cardiac arrhythmia
• No uncontrolled hypertension

Gastrointestinal

• No gastrointestinal tract disease that would preclude taking oral medication
• No active peptic ulcer disease

Other

• Not pregnant or nursing
• Fertile patients must use effective contraception
• No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer
• No history of allergic reaction attributed to compounds of similar chemical or biological composition to sorafenib or other study agents
• No ongoing or active infection
• No psychiatric illness or social situation that would preclude study participation
• No other uncontrolled illness

PRIOR CONCURRENT THERAPY:

Biologic therapy

• See Disease Characteristics
• More than 4 weeks since prior immunotherapy
• No concurrent anticancer immunotherapy
• No concurrent bevacizumab

Chemotherapy

• See Disease Characteristics
• More than 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin) and recovered
• No more than 1 prior chemotherapy regimen for metastatic disease
• No concurrent anticancer chemotherapy

Endocrine therapy

• Prior hormonal therapy in the neoadjuvant, adjuvant, or metastatic setting is allowed
• No concurrent anticancer hormonal therapy

Radiotherapy

• No prior radiotherapy to ≥ 25% of the bone marrow
• More than 4 weeks since prior radiotherapy

Surgery

• More than 4 weeks since prior major surgery
• No prior surgical procedure that would affect gastrointestinal absorption

Other

• No other concurrent drugs that target vascular endothelial growth factor (VEGF) or VEGF receptors
• No concurrent antiretroviral therapy for HIV-positive patients
• No other concurrent investigational agents
• No other concurrent anticancer therapy

• No concurrent cytochrome P450 enzyme-inducing antiepileptic drugs, including any of the following:

  • Phenytoin
  • Carbamazepine
  • Phenobarbital
• No concurrent rifampin
• No concurrent Hypericum perforatum (St. John's wort)

• No concurrent therapeutic anticoagulation

  • Concurrent prophylactic anticoagulation (i.e., low-dose warfarin) for venous or arterial devices is allowed