RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Colony-stimulating factors such as filgrastim may increase the number of immune cells found in bone marrow or peripheral blood and may help a person's immune system recover from the side effects of chemotherapy.

PURPOSE: Phase II trial to study the effectiveness of topotecan, paclitaxel, and filgrastim in treating patients who have previously untreated extensive-stage small cell lung cancer.

OBJECTIVES: I. Evaluate oral topotecan and paclitaxel in terms of toxicity and complete and partial response rate in patients with previously untreated extensive stage small cell lung cancer. II. Determine preliminary estimates of survival in this patient population in response to this regimen.

OUTLINE: Patients receive oral topotecan on days 1-5 followed by paclitaxel IV over 3 hours on day 5. Beginning 24-48 hours after chemotherapy, patients receive filgrastim (G-CSF) subcutaneously daily for up to 10 days until blood counts recover. Treatment repeats every 4 weeks for 6 courses in the absence of disease progression. Patients who develop CNS progressive disease only should receive whole brain radiotherapy before continuing study treatment.

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed previously untreated small cell lung cancer No mixed histology Extensive disease Metastatic disease outside the chest Contralateral supraclavicular nodes or contralateral hilar nodes outside a single radiation port OR Cytologically proven malignant pleural effusion Measurable or evaluable disease No untreated CNS metastases CNS metastases previously treated with whole brain radiotherapy allowed

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: AST no greater than 5 times upper limit of normal (ULN) Alkaline phosphatase no greater than 5 times ULN Total bilirubin no greater than 1.5 times ULN OR Direct bilirubin normal Renal: Creatinine no greater than ULN OR Creatinine clearance at least 50 mL/min Cardiovascular: No uncontrolled angina pectoris No congestive heart failure within the past 3 months, unless ejection fraction greater than 40% No uncontrolled arrhythmias No myocardial infarction within the past 3 months Other: No significant infection No hypersensitivity to E. coli derivatives No other malignancy within the past 3 years except nonmelanoma skin cancer, carcinoma in situ of the cervix, or localized prostate cancer Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 10 years since prior chemotherapy No prior nitrosourea based chemotherapy Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics At least 10 years since prior thoracic radiotherapy No more than 3 fractions of prior thoracic radiotherapy for superior vena cava syndrome Prior palliative radiotherapy except to the chest allowed No prior radiotherapy to at least 20% bone marrow No concurrent radiotherapy (including thoracic), except whole brain radiotherapy for CNS progression Surgery: At least 3 weeks since prior major surgery