Cancer Stem Cell Markers and Prognostic Markers in Circulating Tumor Cells

The study will enroll patients with metastatic colorectal cancer receiving chemotherapy. A total of approximately 22 cc of blood will be drawn during various chemotherapy infusions. Additional proposed laboratory studies may unravel important biological insights into the relationship of circulating tumor cell 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 circulating tumor cells or those with early relapse of circulating tumor cells after early reduction of circulating tumor cell numbers.