Gemcitabine +/- Imatinib Mesylate, Patients w/Previously Treated Metastatic Breast Cancer

DISEASE CHARACTERISTICS:

Histologically confirmed breast cancer

Locally advanced or metastatic disease

Disease progression after at least 1 prior chemotherapy regimen for metastatic disease

No more than 2 prior chemotherapy regimens for metastatic disease (prior neoadjuvant or adjuvant treatment will not be included in determining the number of prior chemotherapy regimens)
Measurable disease

No known symptomatic or untreated brain metastases or carcinomatous meningitis

Previously treated and clinically stable brain metastases allowed provided patient has been off steroids for > 7 days
Hormone receptor status not specified

PATIENT CHARACTERISTICS:

Male or female
Menopausal status not specified
ECOG performance status 0-2
Life expectancy ≥ 3 months
Absolute neutrophil count ≥ 1,500/mm^3
Platelet count ≥ 100,000/mm^3
Bilirubin ≤ 1.5 times upper limit of normal (ULN)
AST or ALT ≤ 2.5 times ULN
Creatinine ≤ 1.5 times ULN OR creatinine clearance ≥ 60 mL/min
Not pregnant or nursing
Negative pregnancy test
Fertile patients must use effective contraception during and for 3 months after completion of study therapy
Able to swallow oral medication
No coexisting medical condition that would preclude study compliance

No uncontrolled illness, including any of the following:

Symptomatic congestive heart failure
Unstable angina pectoris
Cardiac arrhythmia requiring therapy
Myocardial infarction within the past 6 months
Active infection
No New York Heart Association class III-IV cardiac disease
No history of allergic reaction attributed to compounds of similar chemical or biologic composition to gemcitabine hydrochloride and/or imatinib mesylate
No other primary malignancies within the past 5 years except for carcinoma in situ of the cervix or nonmelanoma skin cancer
No known chronic liver disease (i.e., chronic active hepatitis or cirrhosis)
No known HIV infection

PRIOR CONCURRENT THERAPY:

See Disease Characteristics
Recovered from all prior therapy
More than 2 weeks since prior surgery
At least 2 weeks since prior hormonal therapy
At least 2 weeks since prior trastuzumab (Herceptin®)
At least 3 weeks since prior chemotherapy (6 weeks for nitrosoureas)
At least 3 weeks since prior anti-vascular endothelial growth factor therapy
More than 28 days since prior investigational agents

At least 3 weeks since prior radiotherapy

Must have evidence of ≥ 1 measurable target lesion outside the irradiated fields OR radiologically confirmed disease progression within the irradiated fields after completion of radiotherapy
No prior imatinib mesylate for metastatic disease
No prior gemcitabine hydrochloride for metastatic disease
More than 6 months since prior adjuvant gemcitabine hydrochloride
No other concurrent investigational or commercial agents

No concurrent therapeutic anticoagulation with warfarin (e.g., Coumadin® or Coumadine®)

Concurrent heparin or low-molecular weight heparin (e.g., Lovenox®) for therapeutic anticoagulation allowed
Concurrent prophylactic warfarin therapy (e.g., mini-dose Coumadin® ≤ 1 mg daily) to maintain catheter patency allowed
No concurrent routine chronic systemic corticosteroids
No concurrent medications that would preclude study compliance