DISEASE CHARACTERISTICS: Histologically or cytologically confirmed non-small cell lung cancer Progressive or relapsed disease after first-line platinum-based chemotherapy Measurable disease No intracerebral metastases (unless asymptomatic, no corticosteroids required, and diagnostic imaging demonstrates no peritumoral edema or progression)

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: WHO 0-2 Life expectancy: More than 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL Hepatic: Bilirubin no greater than 1.25 times the upper limit of normal (ULN) ALT or AST less than 2.5 times ULN (5 times ULN if liver metastases present) No hepatic impairment No risk of hepatitis B transmission Renal: Creatinine clearance at least 60 mL/min Cardiovascular: No currently unstable or uncompensated cardiac conditions Pulmonary: No currently unstable or uncompensated respiratory conditions Other: No risk of HIV transmission No other malignancy within the past 5 years except adequately treated basal cell skin cancer or carcinoma in situ of the cervix No other severe or uncontrolled systemic disease No infectious condition No significant clinical disorder that would preclude study Body surface area at least 1.2 m2 Not pregnant or nursing Negative pregnancy test Fertile patients must use effective barrier contraception for 3 months before, during, and for 3 months after study

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics Endocrine therapy: See Disease Characteristics Radiotherapy: No prior extensive radiotherapy to 30% or more of bone marrow (e.g., whole of pelvis or half of spine) Surgery: Recovered from prior surgery Other: At least 2 weeks since prior systemic anticancer therapy and recovered