This proposed phase II trial will investigate the combination of topotecan/carboplatin in the first-line treatment of patients with extensive-stage SCLC. Topotecan/platinum regimens are emerging as common treatments for patients with extensive-stage disease. This trial will be one of the first clinical trials to evaluate a combination of weekly topotecan and carboplatin in the first-line treatment of extensive-stage SCLC.

Eligible patients will receive treatment with carboplatin and topotecan.

Topotecan 4mg/m2 IV on days 1, 8.

Carboplatin AUC=5 IV day 1 only .

- Cycles are repeated every 21 days for > 4 cycles of topotecan and carboplatin (maximum 6 courses). Restaging studies will be performed every 2 cycles (or 6 weeks.)

Inclusion Criteria:

• Patients must have confirmed small cell lung cancer with extensive stage disease. This includes patients with stage IIIB and IV disease.
• Patients with small cell histology are eligible. Large neuroendocrine or mixed small cell and non-small cell histology are not eligible.
• Patients must have measurable or evaluable disease.
• ECOG performance status 0 or 1.
• Patients must have adequate bone marrow, liver and kidney function
• The patients may have had no previous chemotherapy.
• Patients must be able to understand the nature of the study and give written informed consent.

Exclusion Criteria:

• Patients with limited stage disease. This includes IA, IB, IIA, IIB, and IIIA.
• Age < 18 years old.
• History of a prior malignancy within three years with the exception of skin cancer (excluding melanoma), cervical carcinoma in situ, in situ breast carcinoma or stage A/B prostate cancer.
• Female patients who are pregnant or are breast feeding
• History of acute myocardial infarction or stroke within 6 months.
• Uncontrolled hypertension, unstable angina, New York Heart Association grade II or greater CHF, serious cardiac arrhythmia requiring medication, or grade II or greater peripheral vascular disease.
• Patients who have received other investigational drugs within 28 days.
• Patients with CNS involvement (brain or meningeal). The single exception to this is the patient previously treated for brain metastases with radiation therapy, or surgical excision who has no evidence of active residual metastases on brain MRI at the time of study entry.
• Patients with large neuroendocrine tumor or mixed small cell and non-small cell histology