Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically confirmed platinum-refractory small cell lung
cancer No response or progression during or within 6 months of completing platinum based
therapy Measurable disease No symptomatic brain or leptomeningeal metastases

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: SWOG 0-2 Life expectancy: At
least 12 weeks Hematopoietic: Granulocyte count at least 1,500/mm3 Platelet count at least
100,000/mm3 No hemolytic anemia Hepatic: Bilirubin normal AST no greater than 2.5 times
upper limit of normal Renal: Creatinine no greater than 1.5 mg/dL OR Creatinine clearance
at least 60 mL/min Cardiovascular: No history of cardiac arrhythmias Other: No other
active malignancy requiring concurrent treatment No allergy to sulfonamides Not pregnant
or nursing Negative pregnancy test Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease
Characteristics No more than 2 prior chemotherapy regimens At least 3 weeks since prior
chemotherapy and recovered Endocrine therapy: No concurrent corticosteroids to control
symptoms of brain and/or leptomeningeal metastases Radiotherapy: At least 4 weeks since
prior radiotherapy No concurrent radiotherapy to measurable lesions Surgery: Not specified
Other: No concurrent hypoglycemic agents (including insulin)