Frequently asked questions patients may have about the NHS-Galleri trial results

What is the NHS-Galleri clinical trial?
This cancer screening trial was conducted by GRAIL in partnership with the National Health Service (NHS) in England, a publicly-funded, government-run healthcare system, to study the Galleri test.1

How many people were enrolled, and for how long?
The trial enrolled 142,000 adults ages 50 to 77, making it the largest study of its kind. Participants received annual Galleri testing for 3 years and were followed for an additional year.1

What is a randomized, controlled trial?
A randomized, controlled trial (RCT) is considered the gold standard for clinical evidence. The RCT is used to evaluate how a test works. Participants are randomly assigned to different study groups. In this trial, one group received the Galleri test with standard-of-care screening (breast, colorectal, cervical, and high-risk lung), and the other received standard-of-care screening alone.1

What was the study’s overall purpose?
The study’s main purpose was to determine whether adding the Galleri multi-cancer early detection test to standard-of-care screening in England (for breast, colorectal, cervical, and high-risk lung cancers) could help detect more cancers earlier.1

Cancer detection outcomes were compared between the 2 groups to evaluate the impact of the Galleri test.

What was the trial’s primary goal?
The trial’s primary goal was to understand if the Galleri test could reduce the number of stage III and IV cancers detected after 3 years of annual screening.1

This primary goal was designed in collaboration with the NHS in 2020 and was established to closely align with the NHS’s long-term plan to diagnose more cancers at early stages (I-II).1

In addition to the study’s primary goal, other objectives included reducing stage IV cancers, measuring test performance, and ensuring product safety.1

What were the study results?
While there was a favorable trend toward a reduction in stage III and IV diagnoses at the end of the trial, a statistically significant reduction was not observed in combined stage III-IV diagnoses across 3 screening rounds for the group of 12 deadly cancers.2*

*The twelve cancers include anus, bladder, colon/rectum, esophagus, head and neck, liver/bile-duct, lung, lymphoma, ovary, pancreas, plasma cell neoplasm, and stomach.

Since the primary goal was not met, does this mean the Galleri test
does not work?
Not at all. There were still more stage III cancers and fewer stage IV cancers for trial participants who received annual Galleri testing in addition to standard-of-care screening over a 3-year period, compared to those who only received the standard of care screening.2 There were also more cancers detected in stages I and II for participants who received Galleri testing in addition to standard-of-care screening.2 The Galleri test performs as intended and is a powerful screening tool that enables people to screen for more than
50 cancer types, many of which do not have recommended screening, before symptoms appear. 3,4 The Galleri test has been rigorously tested in clinical studies with almost 400,000 people.5,6

What were the key takeaways from the study?
The Galleri test showed several important and encouraging results in the recent trial2:

  • 4x more cancers detected 
    After 3 years of annual screening with the Galleri test in addition to standard-of-care screening in England,* more than 3 times as many cancers were found compared with standard-of-care screening alone.
  • 68% of Galleri-detected cancers were found at earlier stages
    The Galleri test deteceted 2 out of 3 cancers in stages I,II, and III across a group of 12 deadly cancers.†
  • 26% reduction of stage IV cancer diagnoses 
    Among patients who took the Galleri test in addition to standard-of-care screening for 3 years, there were 26% fewer stage IV diagnoses in a group of 12 deadly cancers† in the third year compared to patients who had standard-of-care screenings* alone.
  • 25% fewer emergency room cancer diagnoses
    The trial also showed fewer cancers were found after emergency room (ER) visits. This is important since nearly half of stage IV cancers are discovered only after sudden, severe symptoms lead to an ER visit.7 Cancers diagnosed through an ER visit have significantly worse outcomes.8
  • Strong test performance and safety
    The results showed strong, consistent test performance, in line with prior clinical studies. No serious safety concerns were reported. 

    * UK SOC screenings include breast, cervical, colorectal, and high-risk lung cancers.
    †Anus, bladder, colon/rectum, esophagus, head and neck, liver/bile-duct, lung, lymphoma, ovary, pancreas, plasma cell neoplasm, and stomach.
     

What do these study results mean for patients? 
The trial suggests that adding the Galleri test annually to recommended cancer screenings could help detect more cancers earlier and reduce the number of stage IV and ER diagnosed cancers.

NHS-Galleri Trial Overview video transcript

0:00 - The NHS-Galleri trial is a study to see if a simple blood test can help us to find more cancers earlier than we currently find them.

0:10 - We know that finding cancer early means that we can then offer more curative treatment options to patients. Current NHS screening programmes only pick up about 6% of all cancers, and that's because there are only screening programmes for cervical, breast, colorectal and lung cancer more recently.

0:27 - So the test that we used in the trial is called the Galleri test. It's a multi-cancer early detection test.

0:34 - This is one of the largest screening trials in history, it's a trial of enormous magnitude and scientific importance, testing whether this multi-cancer early detection test works in a real-world clinical setting. 

0:47 - There were 142,000 participants between the age of 50 and 77, representing, roughly speaking, the population of England, and diverse socioeconomic backgrounds. They were asked to provide three blood samples over two years. So, we used mobile clinics. The clinics were set up in 150 different places. So, we very much wanted to take screening to people and out into the community.

1:15 - This trial is a randomized controlled trial, which means that we have two groups of people, one of which has the screening test and the other doesn't, and then we compare the results of those two groups. So, half of them, 70,000 people, we tested those samples as soon as anyone had a positive test they were referred to the NHS.

1:33 - And then the NHS investigated that and treated it if there was cancer that needed treating. And in the other arm we just stored the blood samples so that we can look at them in the future. So when we set up a trial, we set ourselves a goal. And the goal here was to reduce the number of people who got stage three and stage four cancer over the three and a half year period.

1:56 - We didn't meet that goal, but we saw a lot of other things which are really positive. We saw a substantial reduction in stage four diagnosis. And that was a 20% reduction after the first year. The chances of survival with stage three cancers are significantly higher than the chances of long-term survival with a stage four cancer. We found a 16% increase in the number of cancers diagnosed at stages one and two. And this includes cancer types like ovarian cancer, pancreatic cancer and liver cancer, where we often find them only at the most advanced stage. 

2:35 - We detected four times more cancers with the multi-cancer early detection test compared to the NHS screening alone. Another exciting finding was that were a quarter fewer people who had their cancer diagnosed after presenting in accident and emergency with something major. And it's not good news if that's the way your cancer’s diagnosed. And so the fact that we reduced that by so much, is very promising.

3:03 - Reducing emergency presentations is a key goal in cancer early detection. This test is accurate and very, very few people who don't have cancer have a positive test result. And in the future, we'll be reporting further results on, longer term follow up from our data. And we're reporting the cost-effectiveness of the intervention, of the test. And we'll be reporting on the psychological impacts of having the test and receiving a cancer diagnosis through screening.

3:34 - In a few years time, the researchers will also look at whether using the test could help reduce cancer deaths. I'm really excited by the results here. We really have shown that there’s an opportunity to make a really substantial difference in finding cancers earlier when we can offer treatment options to patients.

3:55 - I think the UK and the NHS can be phenomenally proud of what they've achieved. It recruited in record time. I think the quality of the data is outstanding, and gave us outcome data in a real-world clinical setting. It's a phenomenal achievement.

4:11 - Trials like this used to take 15 years. We've done it in 4 years. And the results demonstrate that there is a clear future for this kind of test. So I'm really grateful to the 142,000 participants for their time and effort in attending the clinics three times.

4:28 - Without them volunteering we wouldn't learn how to make a better screening programme in the future. So, if anyone's listening, thank you very much.

Based on a clinical study of people ages 50 to 79 around 1% are expected to receive a Cancer Signal Detected result, which includes a predicted Cancer Signal Origin. After diagnostic evaluation, around 62% of these people are expected to have a confirmed cancer diagnosis. The Galleri test is prescription-only.

The Galleri test is recommended for use in adults with an elevated risk for cancer, such as those age 50 or older. It is not recommended for individuals who are pregnant, 21 years or younger, or undergoing active cancer treatment. Galleri should be used in addition to routine cancer screening. Galleri does not detect a signal for all cancers. False positive and false negative results do occur.

The Galleri test is recommended for use in adults with an elevated risk for cancer, such as those age 50 or older. The test does not detect all cancers and should be used in addition to routine cancer screening tests recommended by a healthcare provider. The Galleri test is intended to detect cancer signals and predict where in the body the cancer signal is located. Use of the test is not recommended in individuals who are pregnant, 21 years old or younger, or undergoing active cancer treatment.

Results should be interpreted by a healthcare provider in the context of medical history, clinical signs, and symptoms. A test result of No Cancer Signal Detected does not rule out cancer. A test result of Cancer Signal Detected requires confirmatory diagnostic evaluation by medically established procedures (e.g., imaging) to confirm cancer.

If cancer is not confirmed with further testing, it could mean that cancer is not present or testing was insufficient to detect cancer, including due to the cancer being located in a different part of the body. False positive (a cancer signal detected when cancer is not present) and false negative (a cancer signal not detected when cancer is present) test results do occur. Rx only.

The GRAIL clinical laboratory is certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA) and accredited by the College of American Pathologists. The Galleri test was developed — and its performance characteristics were determined — by GRAIL. The Galleri test has not been cleared or approved by the Food and Drug Administration. The GRAIL clinical laboratory is regulated under CLIA to perform high-complexity testing. The Galleri test is intended for clinical purposes

  1. Neal R, et al. Cancers. 2022;14(19):4818. https://doi.org/10.3390/cancers14194818  
  2. Swanton C, et al. NHS-Galleri: primary results from a randomised controlled trial to assess
    the clinical utility of a multi-cancer early detection (MCED) test in population screening [presentation]. ASCO Annual Meeting; 2026 May 30; Chicago.
  3. Klein EA, et al. Ann Oncol. 2021;32(9):1167-77.
  4. Schrag D, et al. Lancet. 2023;402(10409):1251-60.
  5. GRAIL, Inc. Sponsor/Collaborator: GRAIL, Inc. ClinicalTrials.gov [cited 2025 Jul 17]. https://clinicaltrials.gov/search?spons=GRAIL,%20Inc.&sort=StudyFirstPostDate&viewType=Table