To date, only one publication has reported on the presence of CTCs in SCLC. These investigators used RT-PCR to amplify CK19 cDNA. CTCs were detected in 27% of patients. In our preliminary study using the CellSearch system we have detected 1 or more CTCs in 11/13 (84%) patient samples in various stages of their disease. Thus CTCs may be a promising biomarker but we need more studies. Thus, our first goal is to determine if CTCs in SCLC can predict response to chemotherapy, predict early relapse or function as a as a prognostic marker.