RATIONALE: Biological therapies such as ZD 1839 may interfere with the growth of tumor cells and slow the growth of prostate cancer.

PURPOSE: Phase II trial to study the effectiveness of ZD 1839 in treating patients who have recurrent prostate cancer.

OBJECTIVES: I. Determine the percentage of patients with recurrent prostate cancer experiencing at least a 50% decline in prostate-specific antigen (PSA) after receiving ZD 1839. II. Determine the duration of PSA decline in patients treated with this drug. III. Determine the safety profile of this drug in these patients. IV. Determine the quality of life of patients treated with this drug. V. Determine the time to progression in patients treated with this drug. VI. Correlate epidermal growth factor receptor expression with PSA decline and time to progression in patients treated with this drug.

OUTLINE: This is a multicenter study. Patients receive oral ZD 1839 twice daily on day 1 and once daily on days 2-28 of the first course and then once daily on days 1-28 of subsequent courses. Courses repeat every 28 days for 6 months in the absence of disease progression or unacceptable toxicity. At the discretion of the pharmaceutical company, patients who show evidence of prostate-specific antigen response may continue on ZD 1839 as long as they demonstrate benefit from this treatment extension. Quality of life is assessed at baseline, before each study course, at completion of study, and then annually during the treatment extension (if applicable). Patients are followed every 8 weeks.

PROJECTED ACCRUAL: A total of 45 patients will be accrued for this study.

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed recurrent prostate cancer No metastatic disease (pelvic lymph nodes are considered metastatic disease) Surgically castrated OR Medically castrated (testosterone less than 50 ng/mL) Must continue luteinizing hormone-releasing hormone (LHRH) analog therapy Biochemical progression, defined by at least 2 consecutive rising PSA levels (at least 1 week apart) over a prior reference value PSA at least 5 ng/mL

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: WHO 0-1 Life expectancy: At least 6 months Hematopoietic: Neutrophil count at least 1,500/mm3 Platelet count at least 75,000/mm3 Hepatic: No concurrent unstable or uncompensated hepatic disease Bilirubin no greater than 1.25 times upper limit of normal (ULN) ALT or AST no greater than 2.5 times ULN Renal: No concurrent unstable or uncompensated renal disease Creatinine no greater than 2 times ULN Cardiovascular: No concurrent unstable or uncompensated cardiac disease Pulmonary: No concurrent unstable or uncompensated respiratory disease Other: Fertile patients must use effective contraception No concurrent ocular inflammation or infection No new neurologic symptoms or signs consistent with acute or evolving spinal cord compression confirmed by MRI No other severe or uncontrolled systemic disease No other significant clinical disorder or laboratory finding that would preclude study No blood donation during and for 3 months after study

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy except epoetin alfa Chemotherapy: No prior chemotherapy for recurrent prostate cancer No concurrent suramin Endocrine therapy: See Disease Characteristics At least 8 weeks since prior bicalutamide or nilutamide At least 4 weeks since prior flutamide At least 4 weeks since prior megestrol or corticosteroids No prior estramustine for recurrent prostate cancer No concurrent anticancer hormonal therapy except LHRH analog therapy for medically castrated patients Radiotherapy: At least 4 weeks since prior radiotherapy No concurrent radiotherapy Surgery: See Disease Characteristics Recovered from prior oncologic or other major surgery No surgery during or for 1 week after study Other: Recovered from prior anticancer therapy At least 4 weeks since prior ketoconazole, PC-SPES, or saw palmetto No concurrent systemic retinoids No other concurrent anticancer therapy or investigational agents (e.g., coenzyme Q-10, PC-SPES, or saw palmetto) Concurrent intravenous bisphosphonates allowed if initiated before study