Topotecan in Treating Patients With Recurrent Extensive-Stage Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed small cell lung cancer (SCLC) * Recurrent extensive stage disease * No mixed histology * Measurable disease * At least 1 bidimensionally measurable, non-central nervous system (CNS), indicator lesion confirmed by CT scan or MRI * Sensitive disease * Responded to prior first-line therapy AND relapsed ≥ 60 days after response (90 days after initiation of first-line therapy) * Eligible for high-dose chemotherapy * No symptomatic brain metastases affecting performance status PATIENT CHARACTERISTICS: Age * 18 and over Performance status * Eastern Cooperative Oncology Group (ECOG) 0-2 Life expectancy * At least 2 months Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 9.0 g/dL * Hematocrit \> 35% (without transfusion) Hepatic * Serum glutamic-oxaloacetic transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) ≤ 2 times normal\* * Alkaline phosphatase ≤ 2 times normal\* * Bilirubin ≤ 2.0 mg/dL * Albumin \> 2.5 g/dL * Hepatitis B surface antigen negative * No significant hepatic disease Note: \*≤ 5 times upper limit of normal if liver metastases are present Renal * Creatinine clearance ≥ 40 mL/min Cardiovascular * No history of cardiac arrhythmias * No congestive heart failure * No ischemic heart disease * No stroke or other embolic disease requiring daily treatment that would preclude study participation Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for 3 months after study participation * HIV negative * No known seizure disorder * No active infection requiring systemic therapy within the past 2 weeks * No known hypersensitivity to topotecan hydrochloride * No medical or psychiatric condition that would preclude study participation * No other malignancy except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or stage A low-grade prostate cancer PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * See Disease Characteristics * More than 4 weeks since prior antineoplastic and/or myelosuppressive chemotherapy * No more than 1 prior chemotherapy regimen (except for adjuvant chemotherapy) for SCLC * No prior topotecan hydrochloride Endocrine therapy * Not specified Radiotherapy * Not specified Surgery * Not specified Other * More than 2 months since prior investigational agent * No other concurrent investigational agent