Researchers are studying tests called liquid biopsies, which can provide vital information about cancer genes using only a blood sample.
A blood test to find cancer even before it shows any symptoms is the dream of cancer doctors everywhere.
Researchers at Memorial Sloan Kettering Cancer Center (MSK) are among those hard at work on developing a test that can accurately pick up signs of a tumor anywhere in the body by analyzing bits of DNA in the bloodstream. Such a test could find cancers at their earliest stage, when they’re easier to treat. This is very important for cancers such as pancreatic cancer and ovarian cancer, which don’t have good screening tests and usually are not found until they’re very advanced.
There are many possible uses for this new type of cancer blood test, which is also called a “liquid biopsy”:
- Identify unknown cancers
- Diagnose tumors
- Guide cancer treatment
- Monitor how well therapy works
- Find cancer when it comes back after treatment
So far, there isn’t a reliable blood test for cancer for screening all kinds of people. But liquid biopsies are being used to help guide treatment in people already diagnosed with cancer. The pace of liquid biopsy development is moving fast.
Here’s what we know — and what we’re working on — to realize the promise of blood tests for cancer.
What Are Liquid Biopsies for Cancer?
A liquid biopsy is a blood test that aims to provide the same kind of detailed genetic information as a tissue biopsy on a solid tumor. It reveals important insights about a cancer’s DNA, which often suggest which treatments are most likely to work best.
One key benefit of liquid biopsies is they only need a blood draw, so they are much less invasive than regular tissue biopsies. To biopsy a solid tumor, we must get a sample of cancer cells either through surgery or by putting a needle into the tumor.
How Do Liquid Biopsies Work?
When cancer cells break down, they release fragments (tiny bits) of their DNA into the bloodstream. This genetic material is called circulating tumor DNA (ctDNA).
Liquid biopsies work by finding ctDNA in the blood, even at very low levels, thanks to new technology. The ctDNA fragments, also sometimes called cell-free DNA (cfDNA), can give us valuable information about the genetic mutations (changes) causing the cancer.
There’s another advantage to liquid biopsies. This test picks up critical details in the bloodstream, no matter where the tumor is in the body. Liquid biopsies provide information about tumors that can’t be biopsied because of their location. They also give us information about tumors that are too small to show up on scans.
How and When Are Liquid Biopsies Used at MSK?
At MSK, the most common liquid biopsy test used is called MSK-ACCESS®.
MSK-ACCESS finds mutations in 146 genes that are linked to cancer. Knowing which gene mutations a tumor has helps doctors match people with the best therapies for their particular cancer, such as targeted therapy and immunotherapy treatments that are aimed at the tumor’s mutations.
Diagnosing Cancer Using Liquid Biopsies
We often use MSK-ACCESS when a tumor is hard to reach for a biopsy, or when a person has many tumors in different parts of the body. MSK-ACCESS also can give more information about tumor genetics for people who have been tested with MSK-IMPACT®, a test used to identify genetic mutations in solid tumors.
How Liquid Biopsies Are Used During Cancer Treatment
For people who are in treatment, we often use MSK-ACCESS or another liquid biopsy to monitor how well a drug is working. For example, if someone keeps having high ctDNA levels after starting a treatment, their doctor may decide to try a different therapy. These tests can also tell us if the tumor’s genetics are changing and becoming resistant to a drug, suggesting that another drug may work better.
Using Liquid Biopsies After Cancer Treatment
After treatment ends, a liquid biopsy test like MSK-ACCESS can provide an early warning that a cancer may be coming back. The ctDNA may be found in the blood months or even years before new tumors would be visible on scans.
Can Liquid Biopsies Be Used To Find Cancer Before It’s Diagnosed?
Scientists are currently studying whether they can develop reliable blood tests that would detect cancer in people who don’t yet have any signs or symptoms of cancer. A general blood test for cancer could revolutionize treatment by catching cancer earlier, before it spreads and becomes harder to treat.
One cancer blood test in development is called Galleri, but it is not approved by the U.S. Food and Drug Administration (FDA).
For a screening test to work, it must have high sensitivity — meaning it can find ctDNA or cfDNA even at very low levels. The test must also have high specificity — meaning that it finds only cancer and not other conditions. A test that does not have high specificity can lead to unnecessary follow-up tests, as well as stress and worry.
Current MSK Research on Cancer Liquid Biopsies to Detect Cancer Early
There has been some progress on a blood test to detect cancer early. One recent pilot study led by Deb Schrag, MD, MPH, Chair of MSK’s Department of Medicine, showed the promise of a single blood test that could screen for many types of cancer at the same time. The study, which was published in The Lancet, used an earlier version of Galleri.
- The study enrolled more than 6,600 people who did not have outward signs of cancer.
- Overall, a possible sign of cancer was found in 92 people — about 1.5% of those screened.
- For one-third of those people, more tests confirmed they had cancer.
- The other two-thirds who had a possible sign of cancer did not turn out to have cancer. This is called a false positive.
- Some of the cancers found were types not likely to show up during routine physical examination or current screening. They include cancers of the bile duct, small intestine, and pancreas.
It’s encouraging to see that cancer was detected with a blood test in many people who had no cancer symptoms, but there are still too many false positives to justify testing a broad population of people who have an average risk of cancer.
We’re still refining and studying these blood tests, and there are clinical trials that aim to enroll tens of thousands of people and follow them for many years. For now, MSK doctors don’t recommend liquid biopsy tests to screen most people, unless someone is part of a clinical trial that’s studying how well a test works.
How Are ctDNA Tests Different From Other Blood Tests That Look for Cancer?
For some types of cancer, blood tests have been used for screening for many years. These blood tests are different from the new liquid biopsies because they mainly look for certain proteins instead of cancer DNA.
PSA Tests for Prostate Cancer
The prostate-specific antigen (PSA) test measures the blood level of a protein made by cells in the prostate gland. A high or rising PSA level may show a problem with the prostate. But it doesn’t always mean someone has prostate cancer. In fact, most men with a high PSA level do not have prostate cancer.
PSA tests are an important part of screening guidelines for prostate cancer. If repeated PSA test results are high or rising, we may recommend a biopsy of the prostate tissue to learn whether there is cancer.
CA-125 Tests for Ovarian Cancer
CA-125 is a protein on the surface of many ovarian cancer cells and some other cancer cells. CA-125 can also be found in small amounts in normal tissues. CA-125 blood tests are sometimes used for people who already were treated for ovarian cancer, to look for signs the cancer may be coming back.
CA-125 has also been studied as a way to screen for ovarian cancer in people who have a higher risk. But the test has a lot of false positives as well as false negatives. For that reason, its use is limited. People with CA-125 results that suggest they may have cancer need more testing.
Blood Tests for Colorectal Cancer
The FDA recently approved a liquid biopsy test called Shield to screen for colorectal cancer in people who are at average risk. However, experts at MSK don’t recommend Shield. It can detect later-stage cancers, but it does not work very well at finding early-stage cancers and misses most precancerous polyps.
Are Liquid Biopsy Tests More Commonly Used for Certain Types of Cancer?
Because liquid biopsy tests detect gene mutations that guide the use of targeted therapies, they most often are used for cancers that are regularly treated with targeted therapies. For example, people with lung cancer often have blood tests to tell how well their treatment is working.
When cancer has metastasized (spread) to bones or multiple organs, a liquid biopsy can give a more complete genetic snapshot of all tumors in the body.
Researchers at MSK are continuing to study liquid biopsies to improve the early detection, diagnosis, and treatment of cancer. They’re hopeful that in the coming years, reliable ctDNA screening cancer blood tests will become a part of standard medical checkups. Additionally, new blood tests that are being studied may lead to other ways to find cancer beyond looking at ctDNA.
Liquid Biopsies and Other Blood Tests for Cancer: Key Takeaways
- MSK is researching the use of blood tests for cancer — known as “liquid biopsies” — to find early-stage cancer, before symptoms start.
- Liquid biopsies are currently used to monitor how well cancer treatments are working.
- The hope for cancer blood tests is to find unknown cancers, diagnose tumors, guide cancer treatment, monitor how well a therapy is working, and tell if a cancer may have come back.
- When cancer cells break down, they release bits of their DNA into the bloodstream. These circulating tumor DNA (ctDNA) and cell-free DNA (cfDNA) fragments can be detected by liquid biopsies.
- Liquid biopsies can find ctDNA in the blood even at very low levels.
- MSK-ACCESS® is a cancer blood test that finds mutations in 146 genes linked to cancer and can guide targeted treatments and immunotherapies.
- After cancer treatment, a liquid biopsy test like MSK-ACCESS can provide an early warning that a cancer may be coming back, months or even years before new tumors would show up on scans.