A Multicenter Pilot Study Examining the Role of Circulating Tumor Cells (CTCs) as a Blood-based Tumor Marker in Patients With Small Cell Lung Cancer (SCLC)

Small cell lung cancer (SCLC) is characterized by early dissemination through the blood system with the majority of patients succumbing to their disease in 9-11 months. Despite evaluation of multiple new agents a platinum doublet has remained the standard of care for over 25 years. We believe that the lack of understanding of the biology of SCLC has contributed to our failure to advance treatment and prolong survival. Tumor and blood biomarkers have been shown to be a powerful tool for increasing our understanding of the complex biology of cancer and determining prognosis and response to therapies. Currently, there are no validated biomarkers for response or to follow disease activity in SCLC. Detection of Circulating Tumor Cells (CTCs) is a laboratory technique that became available in the last few decades. Newer, more sensitive technology for the isolation and characterization of CTCs using a rare event imaging system with automated fluorescence microscopy known as CellSearch has demonstrated value in several cancers. CTCs detection by this system is approved as a prognostic biomarker in metastatic breast cancer, and as a tool to monitor disease in metastatic colorectal cancer and castrate resistant prostate cancer.

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.

In addition, we will explore the feasibility of extracting genetic material from CTCs for genomic profile that could immensely help us unravel the complex molecular pathways and gene expression in SCLC, which ultimately will lead to novel drug development. Other investigators have shown that gene expression profiles for CTCs may be used to distinguish normal donor from advanced cancer patients and differentiate among different types of cancers.

In summary, SCLC kills 45,000 Americans each year. The treatment of SCLC has not changed since the introduction of cisplatin and etoposide during 1970s. Research in cancer biology has identified several genetic alterations that could be of therapeutic importance. Novel agents that target these genetic alterations are currently in development. Patient selection will be key in order to determine the activity of these agents. Understanding the biology of this disease is the key to successful interventions and personalizing therapy.