Cancer Stem Cell Markers and Prognostic Markers in Circulating Tumor Cells

Metastatic colorectal cancer (mCRC) has a five year survival of \<10% and is the cause of death of nearly 50,000 individuals in the United States each year. Current first and second line therapies for mCRC include FOLFOX, XELOX, or FOLFIRI in combination with Bevacizumab or Cetuximab or Panitumumab, as well as Xeloda, camptosar or infusional 5-FU within various less intensive regimens for patients who cannot tolerate full-dose chemotherapy. Current practice involves evaluation of response by imaging at 2-3 months after initiation of therapy. Recent studies have demonstrated that the number of circulating tumor cells (CTCs) in the blood of patients with mCRC has independent prognostic value in terms of reflecting disease burden as well as indicating response to therapy. The use of CTC counts offers the possibility of predicting response in treated patients at an earlier time than through standard means by using CT scans. The investigators hypothesize that subsets of CTCs with cancer stem cell (CSC) markers or other known prognostic markers may improve the prognostic value of CTC evaluation in the course of therapy of patients with mCRC. The protocol will use Veridex CellSearch technology and will when possible compare this to other emerging technologies including microfluidic devices that can isolate CTCs or GFP-expressing adenoviruses that replicate in telomerase-expressing epithelial tumor cells ex-vivo. The protocol will enroll 200 patients with metastatic colorectal cancer receiving therapy. Additional proposed laboratory studies may unravel important biological insights into the relationship of CTC genomic and genetic profiles as they compare to the primary tumors. Additionally the investigators hope to gain an understanding of potential subgroups of patients that have very high numbers of CTCs or those with early relapse of CTC after early reduction of CTC numbers. The impact of this research may be in better prediction of response to mCRC therapy so that patients can be treated with second line or other experimental therapy if they are unlikely to respond to their current therapy as predicted by CTC evaluation.