What are CTCs?
Circulating tumor cells (CTCs) are cells that have broken away from a primary tumor and enter the bloodstream. Some CTCs may manage to squeeze out of blood vessels, settle in a new tissue or organ and begin the growth of a metastatic tumor.
There a few different types of CTCs:
- Traditional CTCs are very obvious — they are large and irregular and they display cytokeratin and CD45 on their surfaces, two common molecular markers that indicate cancer.
- Cytokeratin negative CTCs lack cytokeratin and CD45. But they are similar in size, shape, and protein and gene expression as most cancer cells.
- Small CTCs have cytokeratin and CD45, but blend in with other blood cells because they are smaller than traditional CTCs.
- CTC Clusters are multiple attached CTCs. The clusters may be made up of any of the cell types above.
- Apoptotic CTCs are in the process of dying, in a careful, systematic process of cellular shutdown known as apoptosis.
How are CTCs detected?
Finding CTCs in the bloodstream is a bit like finding a needle in a haystack — there may be very few CTCs among millions of normal blood cells. Only over the last few years have new technological advances begun to allow scientists to detect those rare CTCs.
Epic Science’s platform for detecting CTCs uses a simple blood sample. The sample is spread on a microscope slide and stained with dyes that stick to certain molecular features of CTCs. Then we read the slides with a fluorescent scanner. Our software analyzes the scans for more than 90 features on all three million cells in the blood sample. The program picks out cells that might be CTCs and they are confirmed by a specially trained scientist. (To learn more, go deep into the technology.)
What do CTCs tell a doctor about a patient’s cancer?
The mere presence of one or more CTC type described above can give us clues about a cancer’s origin, metastatic risk, and prognosis.
In addition, there are a number of other helpful details we can glean from studying CTCs further. First, we can analyze all of the genes and proteins that make up a patient’s own CTCs. Secondly, we can check for known biomarkers — molecular clues that might help us know more about the type of cancer and choose an appropriate treatment course. For example, there are some types of breast cancer that respond better to a particular drug than others.
Best of all, since the Epic platform uses a simple blood test rather than an invasive biopsy, we can keep re-checking CTCs to determine if and when a tumor has evolved. All of this information helps provide a more precise, personalized treatment course that’s tailored to the individual patient and his or her cancer, as it changes over time.
November is Lung Cancer Awareness Month, learn how CTC research can make a difference in lung cancer.