Galleri multi-cancer early detection (MCED) blood test
Research in England and Wales is looking at a new blood test to see if it can detect a range of cancers. This is called the Galleri multi-cancer early detection test. Or the Galleri blood test for short.
Early research has been promising. Large trials are now taking place to find out more. This test is not available in the UK outside of a clinical trial.
A company called GRAIL Bio UK Ltd makes the Galleri blood test.
The NHS Galleri screening trial is looking at the test in people who do not have cancer. The SYMPLIFY study looked at the Galleri test in people with possible cancer symptoms. Both the trial and study have now closed to recruitment. The SYMPLIFY study now has some results.
What the Galleri blood test looks for
The test looks for abnormal 
in the blood. The cells in our body release DNA that circulates in the blood. There are differences in the DNA of healthy cells and cancerous cells. The test aims to pick up these differences. Your blood is tested for signals that might mean you have cancer.
The researchers hope this test will pick up cancers at an early stage. Diagnosing cancer early means there is a greater chance of successful treatment.
The NHS Galleri screening trial
This trial is the result of a partnership between NHS England and GRAIL. It has now closed to recruitment. The trial team used NHS records to search for people aged 50 to 77 who had:
- not been diagnosed with cancer in the last 3 years, or
- not been treated for cancer in the last 3 years
People in some parts of England received an invitation by letter to join. The trial team hoped to recruit 140,000 people.
Everyone taking part had 3 blood tests over the course of 2 years. This was a randomised trial. This means that those taking part were put into one of two groups by a computer:
- half the people had their samples tested using the Galleri test - this is the test group
- the other half didn’t have the Galleri test and their blood samples were stored, they may be tested in the future - this is the control group
A test result that picks up a cancer signal is also called a positive Galleri test result. This does not mean that a person definitely has cancer. It means that they may have cancer. People who tested positive were referred to see a specialist or to have further tests.
The benefits and risks of taking part
Taking part in a trial like this could benefit others in the future. The trial results may show that the Galleri test is able to pick up cancer early, when it is easier to treat. This in turn will help treat more cancers successfully.
The Galleri test is not perfect and can give a wrong result. This could cause anxiety in those taking part. Some people may have had unnecessary tests if it was found that they didn't have cancer.
The results of the NHS Galleri Screening trial are expected in 2026.
The SYMPLIFY study
This study looked at the Galleri test in people with possible cancer symptoms. It has now closed to recruitment.
Everyone in the study had tests to check for cancer in the usual way. They also gave a sample of blood which was tested with the Galleri test. The results of this study were first published in 2023. Further results were announced at a conference in 2025.
The team concluded that the Galleri test could be useful for helping to diagnose cancer in people with symptoms. Of the 323 people who had a positive Galleri test:
- 244 of them (76%) had cancer - a true positive result
- 79 of them (24%) did not have cancer - a false positive result
The team looked at the number of people with a negative Galleri test who didn’t have cancer. Of the 5,093 people who didn’t have cancer, nearly everyone (98%) had a negative Galleri test.
The study also focused on the 79 people who were not diagnosed with cancer but who had a positive Galleri test. They found that 28 of these 79 people (35%) were diagnosed with cancer within 2 years. This suggests that people should have further follow up appointments and tests to check for cancer if they:
- had a positive Galleri test
- have symptoms that may be caused by cancer
- have not been diagnosed with cancer
Research in other countries
The Galleri blood test is also being looked at in trials in America and Canada.
A trial called PATHFINDER looked at using the Galleri test in over 6,000 people. They did not have cancer or any possible symptoms of cancer. The results showed that some people who had a positive Galleri test were then diagnosed with cancer.
Another trial called PATHFINDER2 has now been carried out, and the results are being analysed. About 35,000 people have had the Galleri blood test as part of this trial.
In 2025, the team presented the results for the first 25,000 people at a conference. These show that:
- 4 out of 10 people (40%) diagnosed with cancer had a positive Galleri test result
- nearly everyone (99%) who hasn’t been diagnosed with cancer had a negative Galleri test result
The team plan to present more results in the future.
If you have symptoms of cancer
You should contact your doctor if:
- you have any possible signs and symptoms of cancer
- you notice a change that isn't normal for you
- you notice that a change continues or worsens even after you’ve sought help for it
This should be the case, even if you are taking part in this research.
Your GP can refer you to a specialist or to have tests if they think that you might have possible symptoms of cancer.
Cancer screening
It’s very important that you consider cancer screening when invited. Taking part in research like this does not replace cancer screening. There are 3 national screening programmes in the UK:
Lung cancer screening is also recommended for people at high risk of developing lung cancer. This is called targeted lung cancer screening.
Remember cancer screening is for people with no symptoms at all. If you have symptoms, don’t wait for a screening invitation. Contact your doctor as soon as possible.
