The precursors of metastasis: circulating tumor cells (CTC), a new milestone in cancer treatment

In this series, we will learn about circulating tumor cells, which will greatly facilitate early cancer diagnosis. These cells will allow cancer to be diagnosed using very small blood samples instead of biopsies that challenge patients psychologically and anatomically. This method is called liquid biopsy.

Most cancer-related deaths result from cancer cells invading other tissues and organs and disrupting normal bodily function. Examining tumor tissue reveals millions of cells. They contain numerous genetic changes (mutations) causing uncontrolled division and invasion of surrounding tissues. As cancer cells increase in number, they migrate to surrounding organs. A very small proportion enter the blood.

Between 5 and 50 of these tumor cells have been observed in a teaspoon-sized blood sample.

These cells entering the bloodstream are called circulating tumor cells .

Circulating tumor cells are critically important in cancer progression. With the help of certain blood cells, they leave the bloodstream, settle in tissues and organs and begin multiplying. They thus perform the complex, systematic process called metastasis . These cells provide information about the cancer's origin and the mutation causing it. Determining their number in blood also informs us about the course of cancer treatment. It is important to emphasize that blood tests used today cannot detect these cells. To identify them, certain specific biological markers have been discovered.

Experiments have established that many circulating tumor cells have multidrug resistance . Eliminating these cells with conventional cancer drugs is therefore almost impossible. Recent research identifies them as a major cause of cancer recurrence. Because they have also been observed differentiating into other cancer types, some scientific authorities have called them cancer stem cells . The number of studies on these cells has steadily increased.

Current information from research on circulating tumor cells:

• Breast cancer patients with very large numbers of these cells in blood samples have been found to have shorter survival.
• Large numbers of drug-resistant tumor cells in lung cancer patients' blood samples have been found to cause very rapid disease progression.
• Changes in biochemical processes performed by circulating tumor cells have been found to cause cancer progression.

Considering all these findings, these cells appear to play an important role in monitoring cancer during treatment. New-generation devices and techniques have been developed to detect them.

Related Topic:

- In the near future, early cancer diagnosis with a drop of blood will become possible