Gefitinib After Chemotherapy in Treating Patients With Stage IIIB or Stage IV Non-Small Cell Lung Cancer

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed non-small cell lung cancer meeting 1 of the following stage criteria: Stage IIIB Pleural fluid and/or supraclavicular nodes allowed provided patient is not eligible for consolidation radiotherapy Stage IV disease No disease progression after 2-6 courses of prior platinum-containing first-line palliative induction chemotherapy Brain metastases allowed provided patients are asymptomatic after cranial irradiation completed at least 4 weeks ago PATIENT CHARACTERISTICS: Age 18 and over Performance status WHO 0-2 Life expectancy Not specified Hematopoietic Not specified Hepatic Not specified Renal Not specified Pulmonary No history, signs, or symptoms of clinically active interstitial lung disease Patients with chronic, stable, asymptomatic radiographic changes are eligible Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No psychological, familial, sociological, or geographical condition that would preclude study compliance and follow-up No other malignant disease within the past 5 years except basal cell skin cancer or adequately treated superficial carcinoma of the cervix PRIOR CONCURRENT THERAPY: Biologic therapy No concurrent immunotherapy Chemotherapy See Disease Characteristics Recovered from prior chemotherapy (alopecia allowed) No concurrent chemotherapy Endocrine therapy Not specified Radiotherapy See Disease Characteristics Surgery Not specified Other No prior epidermal growth factor receptor inhibitors No concurrent administration of any of the following drugs: Phenytoin Carbamazepine Rifampin Phenobarbital Hypericum perforatum (St. John's wort) No other concurrent anticancer therapy No other concurrent experimental drugs