DISEASE CHARACTERISTICS: Histologically or cytologically confirmed metastatic small cell lung cancer (SCLC) Must have sensitive or refractory disease after first-line chemotherapy Refractory Progressive or stable disease during chemotherapy Relapse after a response during treatment Relapse after a response within 3 months after completing chemotherapy Sensitive Relapse after a response of at least 3 months duration after completing chemotherapy At least 1 measurable lesion No previously irradiated lesions No symptomatic brain or leptomeningeal metastasis

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: WHO 0-1 Life expectancy: Not specified Hematopoietic: Hemoglobin at least 9 g/dL Neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) Alkaline phosphatase no greater than 2.5 times ULN ALT or AST no greater than 2.5 times ULN Albumin at least 2.5 g/dL Renal: Creatinine no greater than 1.5 mg/dL OR Creatinine clearance at least 40 mL/min (60 mL/min if treated with prior cisplatin therapy) Cardiovascular: No congestive heart failure or angina pectoris (even if medically controlled) No myocardial infarction within the past year No uncontrolled hypertension or arrhythmia Other: No other serious illness or medical condition No history of significant neurologic disorder (other than metastatic disease or psychiatric disorder) No uncontrolled infection No other malignancy within the past 5 years except curatively treated nonmelanoma skin cancer, carcinoma in situ or the cervix, or other surgically cured cancer No other condition that would preclude study Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for at least 6 months after study

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior immunotherapy for SCLC and recovered No concurrent immunotherapy Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy (6 weeks for carboplatin at doses of at least 500 mg/m2 or AUC more than 7 mg/mL) and recovered No more than 1 prior chemotherapy regimen No concurrent chemotherapy Endocrine therapy: At least 4 weeks since prior hormonal therapy for SCLC and recovered No concurrent steroids for brain metastasis No concurrent hormonal therapy Radiotherapy: See Disease Characteristics At least 2 weeks since prior radiotherapy and recovered No concurrent radiotherapy except palliative local radiotherapy for non-target lesions Surgery: At least 4 weeks since prior major surgery and recovered Other: At least 30 days since prior investigational drugs and recovered No other concurrent anti-cancer therapy No other concurrent investigational drugs