Trastuzumab and Irinotecan in Treating Patients With HER2/Neu Positive Metastatic Breast Cancer

DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed metastatic breast carcinoma
• Received 1-3 prior chemotherapy regimens for metastatic disease
• Documented progressive disease
• Repeated courses of the same chemotherapy agent alone or in combination are considered a single regimen
• Prior trastuzumab (Herceptin®) alone or with chemotherapy allowed
• Other biologic agents are not considered a chemotherapy regimen
• Measurable disease
• Patients with bone-only disease who are evaluable by tumor markers (e.g., CA15-3, CEA, or CA27.29) are eligible
• Patients must have prior evidence of correlation of disease activity with changes in tumor marker level
• Confirmation of HER2/neu status by a positive test for gene amplification by fluorescence in situ hybridization or 3+ by immunohistochemistry
• Brain metastases allowed if the following criteria are met:
• Brain metastases were previously treated and are currently stable as documented by head CT scan with contrast or MRI within 4 weeks of study entry
• Patients with existing brain metastases should have stability documented by prior imaging ≥ 8 weeks before the baseline scan
• Hormone-receptor status not specified

PATIENT CHARACTERISTICS:

• Menopausal status not specified
• ECOG performance status ≤ 2
• Absolute neutrophil count ≥ 1,000/mm^3
• Platelet count ≥ 100,000/mm^3
• Life expectancy ≥ 12 weeks
• No history of congestive heart failure
• Documented ejection fraction ≥ 45% by MUGA scan or echocardiogram within 1 month of study entry
• Total bilirubin < 3 times upper limit of normal (ULN)
• AST < 3 times ULN (5 times ULN if due to liver involvement)
• Creatinine < 1.5 times ULN
• No history of serious adverse events related to trastuzumab
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No severe, concurrent illness that would prevent compliance with study protocol
• No chronic severe diarrheal illness
• No history of Gilbert's disease or known deficiency in glucuronidation
• No recent or current history of alcoholism or acute viral hepatitis

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• No chemotherapy or hormonal therapy within the past 2 weeks
• Prior or concurrent bisphosphonates allowed
• No prior irinotecan (other camptothecins allowed)
• No concurrent radiotherapy
• No ongoing treatment with any other investigational agent