Gefitinib as First-Line Therapy Followed by Gemcitabine and Cisplatin in Treating Patients With Stage III or Stage IV Non-Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically\* or cytologically\* confirmed non-small cell lung cancer (NSCLC), including any of the following cellular subtypes: * Squamous cell carcinoma * Adenocarcinoma * Large cell carcinoma * Poorly differentiated NSCLC NOTE: \*New biopsies or cytologic specimens required for primary resection specimens older than 2 years * De novo or recurrent disease, meeting 1 of the following stage criteria: * Stage IIIB disease * Malignant pleural effusion OR supraclavicular node involvement (N3) * Not suitable for curative multimodal treatment or surgery * Stage IV disease * Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques OR ≥ 10 mm by spiral CT scan or MRI * Measurable lesion must be outside previously irradiated areas * Immediate chemotherapy is not clinically mandatory * No small cell lung cancer (SCLC) or SCLC combined with NSCLC * No symptomatic and/or untreated brain metastases PATIENT CHARACTERISTICS: Age * 18 and over Performance status * WHO 0-1 Life expectancy * Not specified Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 10.0 g/dL Hepatic * Bilirubin normal * AST or ALT ≤ 2.5 times upper limit of normal (ULN) * Alkaline phosphatase ≤ 2.5 times ULN (5 times ULN in the presence of bone metastases) * No unstable or uncompensated hepatic disease Renal * Creatinine clearance \> 60 mL/min * No unstable or uncompensated renal disease Cardiovascular * No unstable or uncompensated cardiac disease * No myocardial infarction within the past 3 months Pulmonary * No clinically active interstitial lung disease * Asymptomatic patients with chronic stable radiographic changes allowed * No unstable or uncompensated respiratory disease Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for 12 months after completion of study treatment * Able to swallow and retain oral medication * No active infection * No uncontrolled diabetes mellitus * No history of allergic reactions or hypersensitivity attributed to compounds of similar chemical or biological composition to study drugs * No other severe or uncontrolled systemic disease * No other serious underlying medical condition that would preclude study participation * No psychiatric disability that would preclude study compliance or giving informed consent * No other malignancy within the past 5 years except adequately treated nonmelanoma skin cancer or carcinoma in situ of the cervix PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * Prior intrapleural or intrapericardial local chemotherapy allowed * No prior chemotherapy for advanced disease * More than 6 months since prior neoadjuvant or adjuvant systemic chemotherapy for NSCLC Endocrine therapy * Not specified Radiotherapy * See Disease Characteristics * Concurrent palliative radiotherapy allowed (except to brain metastases) Surgery * Not specified Other * No prior epidermal growth factor receptor-targeted therapy for NSCLC * No concurrent use of any of the following CYP3A4 inducers: * Phenytoin * Carbamazepine * Rifampin * Barbiturates * Hypericum perforatum (St. John's wort) * More than 30 days since prior participation in another clinical trial * No other concurrent investigational agent