Combination Chemotherapy in Treating Patients With Extensive-Stage Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed extensive stage small cell lung carcinoma (SCLC) * No prior chemotherapy for SCLC OR * No chemotherapy within 5 years of diagnosis of SCLC * Prior radiotherapy to measurable or nonmeasurable disease field allowed provided radiotherapy was completed at least 6 weeks ago and the disease is demonstrated to be progressing * No clinical signs or symptoms of brain and/or leptomeningeal metastases by CT scan or MRI * Brain and/or leptomeningeal metastases that are asymptomatic on neurologic exam are allowed provided metastases do not require corticosteroid therapy to control symptoms PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * ECOG 0-2 Life expectancy: * At least 3 months Hematopoietic: * Hemoglobin at least 9.0 g/dL * WBC at least 3,500/mm3 * Platelet count at least 100,000/mm3 * Neutrophil count at least 1,500/mm3 Hepatic: * Bilirubin no greater than 2.0 mg/dL * SGOT and SGPT no greater than 2 times the upper limit of normal (ULN) (5 times ULN if liver metastases present) * Alkaline phosphatase no greater than 2 times ULN (5 times ULN if liver metastases present) Renal: * Creatinine no greater than 1.5 mg/dL * Creatinine clearance at least 60 mL/min * No pre-existing renal impairment that would preclude cisplatin use Gastrointestinal: * No clinical evidence of any gastrointestinal (GI) conditions including: * Removal of a portion of the stomach * History of recent obstruction of the GI tract * GI autonomic neuropathy * Ulcerative colitis * Crohn's disease * Malabsorption syndrome * Treatment with cyclosporine that would alter absorption or GI motility * No other conditions that would preclude absorption of oral topotecan Other: * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception for 3 months prior to study, during, and for at least 1 month after study * No active infection * No other prior or concurrent malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or localized low-grade prostate cancer * No other concurrent severe medical problems that would expose the patient to extreme risk or preclude study compliance * No prior allergic reactions to compounds chemically related to study drugs * No pre-existing hearing impairment that would preclude cisplatin use * No overall medical condition for which study drugs would be inappropriate PRIOR CONCURRENT THERAPY: Biologic therapy: * No concurrent immunotherapy for SCLC Chemotherapy: * See Disease Characteristics * No other concurrent chemotherapy for SCLC Endocrine therapy: * See Disease Characteristics * No concurrent hormonal therapy for SCLC Radiotherapy: * See Disease Characteristics * At least 24 hours since prior radiotherapy with no expected bone marrow suppression * Recovered from prior palliative radiotherapy (e.g, nausea and vomiting from radiation of the epigastrium) * No concurrent radiotherapy for SCLC * No concurrent radiotherapy for palliation of bone metastases or CNS lesions unless approved by the investigator Surgery: * At least 3 weeks since prior major surgery (a shorter period is allowed if deemed in the best interest of the patient) Other: * More than 30 days or 5 half-lives (whichever is longer) since prior investigational drugs * No other concurrent investigational therapy for SCLC * No concurrent cyclosporine * No concurrent drugs that would preclude absorption of oral topotecan