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