What are Circulating Tumor Cells (CTCs)?
I often get asked what are CTCs (also known as Cell-Free DNA (cfDNA)), JAMA recently published a great article that explains it very nicely. Enjoy!
One of the major challenges in treating cancer is getting “all” of the cancer, including the parts we cannot see. Even if surgery, chemotherapy, or radiation removes all traces of known cancer, there is still a risk of the cancer returning, often in a distant location in the body. This may occur as a result of CTCs.
Circulating tumor cells were first found in the blood under the microscope nearly 150 years ago. They are cancer cells from the primary tumor that escaped into the bloodstream to circulate around the body. As a result, these cells can serve as seeds for new areas of cancer to grow in distant organs. This is known as metastasis.
Not all CTCs have the ability to land and establish a new metastasis in a distant organ; some may remain dormant (inactive) or be controlled by the immune system for years, sometimes forever.
Problems with finding CTCs
Research and clinical applications for CTCs have grown over the past couple of decades. When CTCs are present in the blood, their concentration is very low: as few as 1 CTC per 1 billion red blood cells. A new technique developed in the last few years allows for CTCs to be bound by surface receptors on the cancer cell to antibodies attached to magnetic nanoparticles that can then be separated, counted, and studied further.