ZD 1839 in Treating Patients With Locally Advanced or Metastatic Colorectal Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed colorectal adenocarcinoma * Metastatic or locally advanced disease * Not amenable to curative therapy * Documentation of disease progression within the past 6 months * Previously treated with fluoropyrimidine- and irinotecan-based chemotherapy (including capecitabine) administered either concurrently (no more than 2 regimens) or sequentially (no more than 3 regimens) 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 * No known brain metastases PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * ECOG 0-2 OR * Karnofsky 60-100% Life expectancy: * More than 12 weeks Hematopoietic: * Absolute neutrophil count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 Hepatic: * Bilirubin no greater than 1.5 times upper limit of normal (ULN) * AST/ALT no greater than 3 times ULN (5 times ULN if liver metastasis present) Renal: * Creatinine no greater than 1.5 times ULN OR * Creatinine clearance at least 60 mL/min Cardiovascular: * No symptomatic congestive heart failure * No unstable angina pectoris * No cardiac arrhythmia Ophthalmic: * No significant ophthalmic conditions, including: * Severe dry-eye syndrome * Keratoconjunctivitis sicca * Sjogren's syndrome * Severe-exposure keratopathy * Disorders that may increase the risk for epithelium-related complications (e.g., bullous keratopathy, aniridia, severe chemical burns, or neutrophilic keratitis) Other: * Able to take oral gefitinib * No other uncontrolled concurrent illness * No ongoing or active infection * No psychiatric illness or social situation that would preclude study participation * No prior gastrointestinal disorders (e.g., malabsorption syndrome) * No prior allergic reactions attributed to compounds of similar chemical or biological composition to gefitinib * No other prior malignancy except carcinoma in situ of the cervix, nonmelanoma skin cancer, or other cancer from which the patient has been free of evident disease for more than 5 years and/or has less than a 20-30% estimated likelihood of recurrence * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * See Disease Characteristics * At least 30 days since prior chemotherapy and recovered Endocrine therapy: * Not specified Radiotherapy: * Not specified Surgery: * No prior gastric resection Other: * No other prior therapy for advanced disease * No concurrent combination antiretroviral therapy for HIV-positive patients * No other concurrent investigational or commercial agents or therapies for the malignancy