RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells. 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 combination chemotherapy plus filgrastim in treating patients who have previously untreated extensive-stage small cell lung cancer.

OBJECTIVES: I. Assess the survival and response rate of patients with previously untreated extensive stage small cell lung cancer treated with paclitaxel, carboplatin, topotecan, and filgrastim (G-CSF). II. Determine the side effects and toxicity of this regimen in these patients.

OUTLINE: Patients receive topotecan IV over 30 minutes on days 1-4 and paclitaxel IV over 1 hour followed by carboplatin IV over 1 hour prior to topotecan on day 4. Patients receive filgrastim (G-CSF) subcutaneously once daily beginning on day 5 and continuing until blood counts recover. G-CSF must be discontinued at least 24 hours prior to beginning each subsequent course of chemotherapy. Treatment repeats every 3 weeks for 6 courses in the absence of disease progression or unacceptable toxicity. Patients are followed every 6 months for 3 years.

PROJECTED ACCRUAL: A total of 75 patients will be accrued for this study over 18 months.

• Biological: filgrastim
• Drug: carboplatin
• Drug: paclitaxel
• Drug: topotecan hydrochloride

DISEASE CHARACTERISTICS: Histologically or cytologically proven, previously untreated extensive stage small cell lung cancer (SCLC) Brain metastases allowed if: Asymptomatic OR Previously treated with radiotherapy and/or surgery Measurable or evaluable disease outside the area of prior surgical resection or a new lesion must be present

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: SWOG 0-2 Life expectancy: Not specified Hematopoietic: Absolute granulocyte count at least 1,500/mm3 WBC at least 3,000/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.25 times upper limit of normal (ULN) SGOT or SGPT no greater than 2.5 times ULN Renal: Creatinine no greater than ULN Creatinine clearance at least 50 mL/min Other: Not pregnant or nursing Fertile patients must use effective contraception No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or any stage I or II cancer that is in complete remission

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior systemic biologic therapy for SCLC Chemotherapy: No prior systemic chemotherapy for SCLC Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics No prior radiotherapy for SCLC Surgery: See Disease Characteristics At least 2 weeks since prior thoracic or other major surgery and recovered