DISEASE CHARACTERISTICS: Histologically or cytologically proven, previously untreated extensive stage small cell lung cancer (SCLC) Brain metastases allowed if: Asymptomatic OR Previously treated with radiotherapy and/or surgery Measurable or evaluable disease outside the area of prior surgical resection or a new lesion must be present

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: SWOG 0-2 Life expectancy: Not specified Hematopoietic: Absolute granulocyte count at least 1,500/mm3 WBC at least 3,000/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.25 times upper limit of normal (ULN) SGOT or SGPT no greater than 2.5 times ULN Renal: Creatinine no greater than ULN Creatinine clearance at least 50 mL/min Other: Not pregnant or nursing Fertile patients must use effective contraception No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or any stage I or II cancer that is in complete remission

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior systemic biologic therapy for SCLC Chemotherapy: No prior systemic chemotherapy for SCLC Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics No prior radiotherapy for SCLC Surgery: See Disease Characteristics At least 2 weeks since prior thoracic or other major surgery and recovered