Nitrocamptothecin in Treating Patients With Advanced Small Cell Lung Cancer

DISEASE CHARACTERISTICS: Histologically proven advanced (extensive stage) small cell lung cancer with progressive or recurrent disease after 1 first line chemotherapy regimen Sensitive disease, defined as a response to prior chemotherapy lasting at least 3 months from the end of all prior treatment, including radiotherapy, until the time of progression OR Refractory disease, defined as no response to prior chemotherapy, or a response to prior chemotherapy followed by progression within 3 months after completion of all prior therapy, including radiotherapy Minimum of 1 target lesion that can be accurately measured in at least 1 dimension 20 mm or more with conventional techniques OR 10 mm or more with spiral CT scans No symptomatic brain metastases PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 3 months Hematopoietic: Neutrophil count at least 2,000/mm^3 Platelet count at least 100,000/mm^3 Hepatic: Bilirubin less than 1.5 times upper limit of normal (ULN) Alkaline phosphatase, SGOT, and SGPT no greater than 2.5 time ULN (no greater than 5 times ULN if hepatic metastases present) Renal: Creatinine no greater than 1.7 mg/dL Cardiovascular: No ischemic heart disease within the past 6 months Normal 12 lead electrocardiogram Other: Not pregnant or nursing Fertile patients must use effective contraception No other prior or concurrent malignancy except cone biopsied carcinoma of the cervix or adequately treated basal cell or squamous cell skin cancer No unstable systemic disease or active uncontrolled infection No psychological, familial, sociological, or geographical condition that may preclude compliance PRIOR CONCURRENT THERAPY: Biologic therapy: Prior maintenance therapy with biologic agents following first line chemotherapy allowed No concurrent filgrastim (G-CSF) with nitrocamptothecin Chemotherapy: See Disease Characteristics Greater than 4 weeks since prior chemotherapy No more than 1 prior chemotherapy regimen for extensive disease Alternate or sequential use of different regimens without interruption in first line treatment is considered 1 first line therapy Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics Greater than 4 weeks since prior radiotherapy Surgery: Greater than 2 weeks since prior major surgery Other: No other concurrent anticancer therapy No other concurrent investigational therapy