What is CTCs/DTCs

Tumor formation is thought to be a multi-step process characterized by the gradual accumulation of genetic alterations caused by many environmental and internal (e.g. hormonal) factors acting on organism. The first step toward successful metastases is the detachment of malignant cells from primary tumors caused by the loss of intercellular contacts in the primary tumor, cell motility and local invasivity induction. This transient process is known as epithelial–mesenchymal transition (EMT).
It is characterized by the reduction of epithelial and increased mesenchymal cell traits. Further intravasation into the blood or lymphatic vessels occurs to give rise to circulating tumor cells (CTCs) with their subsequent transport through an organism.

As these cells circulate further in the bloodstream they are known as circulating tumor cells (CTCs). The metastatic process continues by extravasation of CTCs from the circulation and the establishment of a secondary tumor locus in a distant organ with increased metastasis. The CTC population is highly resilient, enabling the cells to colonize a foreign microenvironment.

Single tumor cells occurring in blood circulation are CTCs, while the single tumor cells seeding distant organs prior to detection of metastasis are termed DTCs (disseminated tumor cells).

CTCs and DTCs may be rare events of primary tumor progression. Many clinical studies have been conducted showing the utility of CTC detection in the peripheral blood as a valuable predictor of the clinical outcome for patients with solid tumors.

Detection, monitoring, and molecular analysis of these extremely rare cancer cells (estimated as one tumor cell per billion normal blood cells in patients with diagnosed metastatic cancer) could provide new possibilities in cancer treatment. Over the last decade, various methods and systems have been developed to isolate and characterize CTCs and DTCs, but so far any of the methods has been claimed to be a standard for CTC-separation and detection.