Histopathological examination (biopsy) is the "gold standard" for the diagnosis of
colorectal cancer (CRC). However, biopsy is an invasive method, and due to the temporal and spatial heterogeneity of the
tumor, a single biopsy cannot reveal the comprehensive biological characteristics and dynamic changes of the
tumor. Therefore, there is a need for new
biomarkers to improve CRC diagnosis and to monitor and treat CRC patients. Numerous studies have shown that "liquid biopsy" is a promising minimally invasive method for early CRC detection. A liquid biopsy mainly samples
circulating tumor cells (CTCs),
circulating tumor DNA (ctDNA),
microRNA (
miRNA) and extracellular vesicles (EVs). CTCs are malignant cells that are shed from the primary
tumors and/or
metastases into the peripheral circulation. CTCs carry information on both primary
tumors and
metastases that can reflect dynamic changes in
tumors in a timely manner. As a promising
biomarker, CTCs can be used for early disease detection, treatment response and
disease progression evaluation, disease mechanism elucidation, and therapeutic target identification for drug development. This review will discuss currently available technologies for plasma CTC isolation and detection, their utility in the management of CRC patients and future research directions.