Combination Chemotherapy With or Without Filgrastim in Treating Patients With Previously Untreated Extensive-Stage Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed extensive stage small cell lung cancer * Previously untreated with chemotherapy * No mixed histology * Metastatic disease outside the chest * Contralateral supraclavicular or hilar nodes that cannot be included in a single radiation port OR * Cytologically proven malignant pleural effusion * Measurable disease * No untreated CNS metastases * CNS metastases treated with whole-brain radiotherapy (WBRT) allowed after completion of WBRT PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * ECOG 0-2 Life expectancy: * Not specified Hematopoietic: * Absolute neutrophil count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 Hepatic: * AST no greater than 5 times upper limit of normal (ULN) * Alkaline phosphatase no greater than 5 times ULN * Bilirubin no greater than 1.5 times ULN OR * Direct bilirubin no greater than ULN Renal: * Creatinine no greater than 1.5 times ULN OR * Creatinine clearance at least 50 mL/min Cardiovascular: * No uncontrolled angina pectoris * No congestive heart failure within the past 3 months unless ejection fraction is greater than 40% * No uncontrolled cardiac arrhythmias * No myocardial infarction within the past 3 months Other: * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No clinically significant infection * No hypersensitivity to E. coli-derived proteins * No other malignancy within the past 3 years except non-melanoma skin cancer, carcinoma in situ of the cervix, or localized prostate cancer PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * See Disease Characteristics * At least 5 years since prior chemotherapy for another malignancy * No prior nitrosoureas Endocrine therapy: * Not specified Radiotherapy: * See Disease Characteristics * No prior thoracic radiotherapy * At least 1 day since prior palliative radiotherapy (except to chest) * No more than 3 fractions to chest for superior vena cava syndrome allowed * No concurrent radiotherapy (including thoracic radiotherapy) Surgery: * More than 3 weeks since prior major surgery