Monoclonal Antibody Plus Chemotherapy in Treating Patients With Advanced Colorectal Cancer That Overexpresses HER2

DISEASE CHARACTERISTICS: Histologically confirmed stage IV colorectal cancer with p185 HER2 overexpression Bidimensionally measurable disease Indicator lesion must be outside of irradiated field No symptomatic CNS brain metastases PATIENT CHARACTERISTICS: Performance status: ECOG 0-2 Absolute granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Bilirubin no greater than 1.5 times upper limit of normal (ULN) SGOT no greater than 3.0 times ULN Creatinine no greater than 2.0 mg/dL LVEF at least 45% by MUGA or ECHO No myocardial infarction within the past 6 months No congestive heart failure No unstable angina No clinically significant pericardial effusion or arrhythmia Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 6 months after study No other prior malignancy within the past 5 years, except: Curatively treated basal or squamous cell skin cancer Curatively treated carcinoma in situ of the cervix No active serious infection or serious underlying medical condition that would prevent compliance No dementia or significantly altered mental status PRIOR CONCURRENT THERAPY: Concurrent filgrastim (G-CSF), sargramostim (GM-CSF), or epoetin alfa allowed No prior trastuzumab No more than 1 prior chemotherapy regimen for advanced disease (if progressed during or within 6 months of adjuvant therapy considered to have had 1 regimen for advanced disease) No prior irinotecan Concurrent contraception, estrogen replacement therapy, or megestrol acetate for anorexia allowed Greater than 3 weeks since prior radiotherapy and recovered Greater than 3 weeks since major surgery (except simple biopsy or venous access placement) and recovered At least 3 weeks since prior investigational nonneoplastic drugs