Circulating Tumor Cells (CTC) in Lung Cancer

Inclusion Criteria Cohort A (one-time blood sample) \& Cohort B (multiple blood samples) * Histologically or cytologically confirmed lung cancer (both non-small cell lung cancer and small cell lung cancer are allowed) * Stage 4 NSCLC or extensive-stage SCLC * Newly diagnosed disease with no prior systemic therapy for advanced disease Note: Patients that have received prior adjuvant chemotherapy or prior chemoradiotherapy for earlier stage lung cancer are allowed if treatment was completed ≥3 months. * Age ≥ 18 years * Ability to understand and the willingness to sign a written informed consent document Inclusion of Women and Minorities Both men and women of all races and ethnic groups are eligible for this study.