The Clinical Potential of Circulating Tumor Cells and Circulating Tumor-Associated Cellular Elements in Colorectal Cancer

Colorectal cancer (CRC) remains one of the commonest types of cancer in the USA. Effective treatment and potential curative resection is dependent on early detection, prior to the development of distant metastases. Radiologic and endoscopic evaluations are operator-dependent and limited by macroscopic detection when the relative cellular tumor burden is already high. Also, use of serum biomarkers such as carcinoembryonic antigen may not correlate with the extent of disease involvement. Circulating tumor cells (CTCs) continue be a prominent area of investigation, despite having been described first by Ashworth in 1869. As methods for detection expand and improve, CRC is increasingly characterized by the properties of CTCs and tumor-associated cellular elements (TACEs), such as circulating tumor DNA, cellfree DNA, and microRNA. This review serves to highlight the clinical implications of CRC CTCs and TACEs for prognostication, monitoring for disease recurrence, and response to therapy.