Phase II trial to study the effectiveness of imatinib mesylate in treating patients who have metastatic breast cancer. Imatinib mesylate may stop the growth of cancer by blocking the enzymes necessary for tumor cell growth

PRIMARY OBJECTIVES:

I. To determine the efficacy of STI571 in metastatic breast cancer (MBC) that demonstrates expression of CD117 (c-kit) and/ or PDGFR.

SECONDARY OBJECTIVES:

I. To determine the clinical activity of STI571 in MBC with expression of CD117 (ckit) and/ or PDGFR by evaluating progression-free survival (PFS).

II. To determine the toxicity profile and tolerability of STI571 in patients with MBC.

III. To define serum, tissue and imaging surrogate endpoints of activity of STI571 in MBC.

OUTLINE:

Patients receive oral imatinib mesylate twice daily. Treatment continues for at least 8 weeks in the absence of disease progression or unacceptable toxicity.

Inclusion Criteria:

• Histologically or cytologically confirmed metastatic breast cancer

• Documented expression of CD117 (c-kit) or platelet-derived growth factor receptor

  • Adequate tumor tissue from either the primary tumor and/or metastatic disease available for evaluation

• Must have received prior chemotherapy with an anthracycline (doxorubicin or epirubicin) and/or taxane (paclitaxel or docetaxel) as adjuvant or for advanced disease

• At least 1 unidimensionally measurable lesion

  • At least 20 mm by conventional techniques OR at least 10 mm by spiral CT scan
  • Bone disease may not be only source of measurable disease
  • Pleural or peritoneal ascites are not considered measurable disease

• No known brain metastases

• Hormone receptor status:

  • Not specified

• Female or male

• Not specified

• Performance status - ECOG 0-2

• Performance status - Karnofsky 60-100%

• More than 12 weeks

• Absolute neutrophil count at least 1,500/mm^3

• WBC at least 3,000/mm^3

• Platelet count at least 100,000/mm^3

• Bilirubin normal

• AST or ALT no greater than 2.5 times upper limit of normal

• Creatinine normal

• Creatinine clearance at least 60 mL/min

• No symptomatic congestive heart failure

• No unstable angina pectoris

• No cardiac arrhythmia

• No other uncontrolled concurrent illness

• No ongoing or active infection

• No prior allergic reaction attributed to compounds of similar chemical or biologic composition to imatinib mesylate

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

• No psychiatric illness or social situation that would preclude study compliance

• Not pregnant or nursing

• Negative pregnancy test

• Fertile patients must use effective barrier contraception during and for 1 week after study

• No concurrent biologic agents

• No more than 2 prior chemotherapy regimens for metastatic disease

  • Therapy with high-dose regimens or bone marrow transplantation considered 1 regimen

• At least 4 weeks since prior chemotherapy (6 weeks for carmustine or mitomycin) and recovered

• No concurrent chemotherapy

• Prior hormonal therapy for stage IV disease and/or as adjuvant therapy allowed

• At least 4 weeks since prior radiotherapy and recovered

• Prior localized radiotherapy that does not influence the signal of the evaluable lesion is allowed

• At least 2 weeks since prior minor surgery

• At least 4 weeks since prior major surgery

• Recovered from prior surgery

• Low-molecular weight heparin or heparin allowed for anticoagulation

• No concurrent warfarin

• No concurrent combination antiretroviral therapy for HIV-positive patients

• No concurrent investigational therapies or agents

• No other concurrent anticancer therapy

• No concurrent intake of cola, orange juice, grapefruit, or orange or grapefruit sections