DISEASE CHARACTERISTICS: Histologically confirmed oat cell or intermediate type small cell lung cancer Patients must have received prior therapy, with the following: Documented disease progression (new lesions or increased lesion size) after front line therapy No more than 1 prior chemotherapy regimen Complete or partial response to initial chemotherapy (must have lasted more than 60 days after end of therapy before relapse occurred) Bidimensionally measurable disease At least one lesion outside of irradiation field Pleural effusions are not measurable No brain or bone metastases as only measurable site No uncontrolled brain or other CNS metastases (surgical excision and/or radiotherapy)