Gefitinib in Treating Patients With Recurrent Metastatic Colorectal Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically proven adenocarcinoma of the colon or rectum * Measurable disease * Evidence of new or progressive metastatic disease within 6 months of last treatment * Must have received prior systemic treatment with fluorouracil (and/or its analogs, with or without leucovorin calcium or levamisole) and irinotecan in the adjuvant or metastatic setting * Metastatic tumor site accessible for biopsy * No known brain metastases PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * ECOG 0-2 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 or ALT no greater than 2.5 times ULN (5 times ULN if tumor involvement of the liver) Renal: * Creatinine no greater than 1.5 times ULN OR * Creatinine clearance at least 60 mL/min Cardiovascular: * No New York Heart Association class III or IV heart disease * No symptomatic congestive heart failure * No unstable angina pectoris * No cardiac arrhythmia Other: * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No ongoing active or uncontrolled infections * Other prior malignancies allowed provided prior therapy is discontinued and no evidence of disease * No other uncontrolled illness or psychiatric illness/social situations that would preclude study * Must be able to take and retain oral medications PRIOR CONCURRENT THERAPY: Biologic therapy: * No prior signal transduction inhibitors (e.g., vascular endothelial growth factor-, vascular endothelial growth factor receptor-, and epidermal growth factor receptor-targeted agents) for colorectal cancer Chemotherapy: * See Disease Characteristics * At least 4 weeks since prior chemotherapy and recovered * No other prior cytotoxic chemotherapy (e.g., oxaliplatin) for colorectal cancer Endocrine therapy: * Not specified Radiotherapy: * At least 4 weeks since prior radiotherapy and recovered Surgery: * Not specified Other: * No other prior systemic therapy for colorectal cancer * No other prior investigational or approved agents for colorectal cancer * No other concurrent investigational agents * No concurrent antiretroviral therapy for HIV-positive patients