PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior systemic chemotherapy No other concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics Prior radiotherapy for non-small cell lung cancer allowed Radiotherapy for new brain metastases (other than leptomeningeal disease) is allowed during study, but chemotherapy is stopped during and for 2 weeks following radiotherapy Concurrent radiotherapy to other sites allowed if there is no objective criteria for disease progression Surgery: Not specified Other: No other concurrent experimental drug