Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed adenocarcinoma of the breast

- Clinical manifestations of metastatic disease

- If patient's tumor is HER2 positive (3+ by immunohistochemistry [IHC] or amplified by
fluorescent in situ hybridization [FISH]), must have received at least one prior
trastuzumab (Herceptin)-containing regimen unless there is a contraindication

- Measurable disease defined as at least one lesion whose longest diameter can be
accurately measured

- The only evidence of metastasis must not be bone metastases or other
non-measurable disease

- Nonmeasurable disease is defined as all other lesions, including small lesions
(longest diameter < 2 cm) and truly nonmeasurable lesions which include any of
the following:

- Bone lesions

- Leptomeningeal disease

- Ascites

- Pleural/pericardial effusion

- Inflammatory breast disease

- Lymphangitis cutis/pulmonis

- Cystic lesions

- Abdominal masses that are not confirmed and followed by imaging techniques

- No known CNS metastasis unless controlled by prior surgery and/or radiotherapy

- To be considered controlled, there must be at least 2 months of no symptoms or
evidence of progression prior to study entry

- Hormone receptor status

- Not specified

PATIENT CHARACTERISTICS:

- Men or women

- Menopausal status not specified

- ECOG performance status 0-2

- Life expectancy > 3 months

- Hemoglobin > 8.0 g/dL

- Absolute neutrophil count ≥ 1,500/mm³

- Platelet count ≥ 100,000/mm³

- Creatinine ≤ 1.5 times upper limit of normal (ULN)

- Bilirubin normal

- AST and ALT ≤ 5 times ULN

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must employ adequate contraception (as determined by the treating
physician) during treatment and for 30 days after treatment ends

- Disease-free for ≥ 3 years of other invasive non-breast malignancies (exception:
curatively treated basal cell or squamous cell carcinoma of the skin and carcinoma in
situ of the cervix)

- No history of allergy or hypersensitivity to drug product excipients, murine
antibodies, or agents chemically similar to irinotecan and/or cetuximab

- No history or evidence of Gilbert's syndrome

- No active, unresolved infection

- No New York Heart Association class III or IV cardiovascular disease

- No serious concomitant medical condition that would make it undesirable for patient
to participate in the trial or would jeopardize compliance with protocol treatment

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- No more than 2 prior chemotherapy regimens in the metastatic setting (irrespective of
hormonal therapy or prior trastuzumab therapy)

- Prior treatment in the metastatic or adjuvant setting must have included an
anthracycline or a taxane

- No major surgery ≤ 3 weeks prior to registration

- No chemotherapy ≤ 2 weeks prior to registration

- No radiotherapy ≤ 4 weeks prior to registration

- No prior irinotecan hydrochloride

- No prior therapy with an epidermal growth factor receptor (EGFR) antagonist (either
monoclonal antibody or tyrosine kinase inhibitor), such as gefitinib or erlotinib

- No prior therapy with a dual EGFR/HER2 inhibitor (e.g., lapatinib)

- No concurrent interleukin-11(oprelvekin)

- Routine use of granulocyte colony stimulating factors (CSFs) is not permitted during
course 1 of this study

- Subsequent use of CSFs is permitted at the discretion of the treating
investigator

- No other concurrent antitumor therapy