Irinotecan and Carboplatin in Treating Patients With Newly Diagnosed Extensive-Stage Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed small cell lung cancer * Extensive stage disease * Newly diagnosed, treatment-naive disease * At least 1 unidimensionally measurable lesion * No massive pleural or pericardial effusion by chest CT scan * Manageable effusions allowed PATIENT CHARACTERISTICS: Age * Over 18 Performance status * ECOG 0-2 Life expectancy * More than 3 months Hematopoietic * WBC ≥ 3,000/mm\^3 * Absolute granulocyte count ≥ 1,500/mm\^3 * Hemoglobin ≥ 9.0 g/dL Hepatic * ALT or AST ≤ 2 times upper limit of normal * Bilirubin ≤ 1.5 mg/dL Renal * Creatinine normal Cardiovascular * No myocardial infarction within the past year * No uncontrolled hypertension * No unstable angina * No congestive heart failure * No ventricular arrhythmia requiring medical intervention * No other serious cardiovascular disease Pulmonary * Arterial oxygen pressure (Pa O\_2) ≥ 70 mm Hg * No interstitial pneumonitis or pulmonary fibrosis by chest x-ray Other * Not pregnant or nursing * No uncontrolled diabetes * No severe infection * No paralytic or obstructive ileus * No serious diarrhea * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix that is in complete remission PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * Not specified Endocrine therapy * Not specified Radiotherapy * No prior radiotherapy to the chest * Other prior radiotherapy allowed Surgery * At least 2 weeks since prior surgery and recovered