Many people are scared when they hear the word "biopsy," right? It's normal to feel a little scared when they hear the word "biopsy." But imagine if there was a way to find out about cancer cells by taking just a drop of your blood? That's what we call this amazing, cutting-edge technology, "Liquid Biopsy." This has brought great hope to those fighting cancer.
Simply put, what is this Liquid Biopsy?
Liquid Biopsy is a special blood test that is used to detect tumors. Imagine that when a tumor develops in our body and grows, small pieces of the tumor break off and enter the blood. Just like pieces of plaster falling off an old wall. We can detect the pieces of cancer that enter the blood with this Liquid Biopsy test.
There are two main things that can be present in the blood:
- Circulating tumor cells (CTCs): These are whole cancer cells that have broken off from the tumor and travel throughout the body through the bloodstream.
- Circulating tumor DNA (ctDNA): These are small pieces of genetic information (DNA) inside cancer cells. DNA is like a "blueprint" that contains all the instructions a cell needs to function. When cancer cells die, these pieces of DNA accumulate in the blood.
Having these CTCs or ctDNA in your blood is a good indication that there is cancer somewhere in your body. Also, these pieces of information can give us a great deal of insight into the genetic information of the cancer. Using that information, your doctor can help you decide what treatment is best for you.
This is still a relatively new technology, but scientists believe it could revolutionize cancer treatment. There are already several trials approved by agencies such as the US Food and Drug Administration (FDA).
How is this different from a regular biopsy?
There is a big difference between the two. In a regular biopsy, a tissue sample is taken directly from the cancerous tumor and tested. However, in a liquid biopsy, a sample is not taken from the tumor. Instead, it looks for evidence of cancer (cancer cells or DNA fragments) in the blood.
Let's look at this table to further clarify the difference between the two.
| Feature | Liquid Biopsy | Traditional Biopsy |
|---|---|---|
| How to do it | Very simple. Usually only a small amount of blood is taken. | Sometimes a small operation is performed to remove a piece of tissue from the cancerous tumor. |
| Pain and risk | There is only a slight pain from the needle. The risk is very low. | It can be painful. You have to be anesthetized. There can be risks like infection. |
| What to find | Cancer cells (CTCs) and cancer DNA (ctDNA) fragments in the blood. | The cells of the cancer tumor itself are examined directly. |
| Main use | See how the patient responds to treatment and choose the most appropriate treatment. | First, confirm whether there is cancer or not. |
But it is important to remember this: The best and gold standard method in the world to confirm 100% accurately whether or not cancer is present is the traditional biopsy.
In a liquid biopsy, there is a small chance that even if there is cancer in the body, the blood sample taken at that time will not contain cancer cells. However, if cancer is detected, the information it provides is invaluable for planning treatment.
In what cases is a liquid biopsy performed?
A doctor usually recommends this test for patients whose cancer is more advanced and has spread to other parts of the body (metastatic cancer). This helps them decide what to do next, especially if current treatments are not working well.
There are several main reasons for doing this test:
1. Determine prognosis
The number of CTCs (cancer cells) in the blood can give a rough idea of the patient's condition. A low number of CTCs in the blood means a relatively good condition. However, if there are a lot of CTCs, it means that the disease is a little more severe. In this way, doctors can do this test from time to time, see how the disease is responding to treatment, and change the treatment accordingly.
2. Make treatment decisions
This is one of the most valuable benefits of Liquid Biopsy. Some cancer cells have specific genetic errors. There are specific drugs that target only those changes. We call this ``targeted therapy''. To put it simply, it's like a lock that can only be opened with a specific key. Liquid Biopsy can tell you what kind of "lock" your cancer cells have. Then your doctor can give you the right "key" (drug) for that.
3. If a normal biopsy cannot be performed
Sometimes a patient may be too weak to undergo a regular biopsy. Or the tumor may be in a very sensitive and difficult-to-reach part of an organ, such as the brain or lungs. If a piece is cut from such a place, there is a risk of damaging the surrounding healthy tissue. In such cases, a risk-free liquid biopsy is very useful.
What are the currently approved Liquid Biopsy tests?
There is a lot of research going on around the world. There are currently several major trials that have been approved by the FDA in the United States, meaning that they have been thoroughly tested for safety and accuracy:
- Cell Search® Circulating Tumor Cell (CTC) Test: This measures the number of CTCs (cancer cells) in the blood. It is used to monitor the status of patients with breast, prostate, and colon cancer that has spread throughout the body.
- cobas® EGFR Mutation Test v2: This tests for ctDNA (cancer DNA fragments). It identifies changes in the EGFR gene, which are particularly common in lung cancer (non-small cell lung cancer - NSCLC). Accordingly, the most appropriate `targeted therapy` can be selected.
- Guardant360® CDx: This also looks for ctDNA. It identifies common genetic changes seen in several types of cancer and helps doctors choose the most effective treatment.
- FoundationOne® Liquid CDx: This is also a ctDNA test used to identify genetic changes in various types of cancer, which can help determine the most effective treatments.
Is this test painful? How long does it take to get the results?
The best thing about Liquid Biopsy is that it's a very simple, painless procedure. It's just like giving blood for a regular blood test. There's no pain other than a slight stinging sensation when the needle is inserted.
Your blood sample is sent to a lab, where pathologists separate the plasma from the blood and test it for CTCs or ctDNA. It usually takes two to three weeks to get the results.
The results tell you whether your blood sample contains cancer cells or DNA fragments (positive) or not (negative). If positive, some tests can also find out what type of cancer they are from and what genetic changes they have.
Take-Home Message
- A liquid biopsy is not a procedure that involves cutting a piece of tissue from the body like a regular biopsy. It is done with a simple blood test.
- This looks for small pieces of broken cancer cells (CTCs and ctDNA) that have accumulated in the blood.
- This is mainly used to choose the best treatment for patients with metastatic cancer and to monitor the body's response to treatment.
- This is much less painful and risky than a regular biopsy.
- Most importantly: The best way to first confirm whether or not cancer is present (the gold standard) is a traditional biopsy.
- It's best to talk to your doctor about whether this test is necessary and appropriate for you.
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