ZD 1839 Plus Combination Chemotherapy in Treating Patients With Locally Advanced, Locally Recurrent, or Metastatic Colorectal Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed adenocarcinoma of the colon or rectum * Locally advanced, locally recurrent, or metastatic disease * Not curable by surgery and/or not amenable to radiotherapy with curative intent * Histological or cytological confirmation of metastatic cancer not required for patients with prior surgically resected colorectal cancer if more than 5 years elapsed between primary surgery and development of metastatic disease OR if primary cancer was stage I or II * Prior adjuvant therapy with fluorouracil or immunotherapy for resected stage II, III, or IV disease allowed * Measurable disease * No known brain metastases PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * ECOG 0-1 Life expectancy: * More than 12 weeks Hematopoietic: * WBC at least 3,000/mm\^3 * Absolute neutrophil count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 Hepatic: * Bilirubin normal * AST/ALT no greater than 5 times upper limit of normal Renal: * Creatinine normal Cardiovascular: * No uncontrolled high blood pressure * No unstable angina * No symptomatic congestive heart failure * No myocardial infarction within the past 6 months * No serious uncontrolled cardiac arrhythmia * No New York Heart Association class III or IV heart disease Other: * No active or uncontrolled infection * No predisposing colonic or small bowel disorders with uncontrolled symptoms as indicated by more than 3 loose stools daily in patients without a colostomy or ileostomy * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or adequately treated noninvasive carcinomas * No other concurrent medical or psychiatric condition that would preclude study * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * At least 12 months since prior immunotherapy Chemotherapy: * At least 12 months since prior fluorouracil * No prior chemotherapy for advanced colorectal cancer * No prior irinotecan Radiotherapy: * No prior radiotherapy to more than 15% of bone marrow * At least 4 weeks since prior major radiotherapy (e.g., chest or bone palliative radiotherapy) * No concurrent radiotherapy Surgery: * At least 4 weeks since prior major surgery (e.g., laparotomy) and recovered * At least 2 weeks since prior minor surgery and recovered * No concurrent ophthalmic surgery Other: * No prior ZD 1839 * No other concurrent investigational or commercial agents or therapies for malignancy * No concurrent combination antiretroviral therapy for HIV * No concurrent oral retinoids * No concurrent prochlorperazine on day of irinotecan administration