A man in a car looks down at his phone. “No cancer signal detected,” says a message on the screen. The man closes his eyes and smiles in relief.
This television advertisement, aired during American football’s Super Bowl in February 2026, promotes a simple blood test that promises to detect the early signs of more than 50 cancer types — or provide the reassurance of an all-clear.
The test, called Galleri, is one of around 40 such Multi-Cancer Early Detection (MCED) tests that are either in development or already on sale. However, very few have been through Randomized Controlled Trials (RCTs) — which are considered the gold standard of testing — and none has received approval from regulators.
In February 2026, the developers of the Galleri test, biotechnology company Grail in Menlo Park, California, released some details from the first RCT of an MCED test. The trial, run in collaboration with the UK National Health Service (NHS), aimed to find out whether Galleri can improve outcomes by reducing the number of cancers detected at advanced stages, when used alongside existing screening programs — however, the results indicate that the test did not meet this goal.
The science that powers these tests is not new: researchers have long known that markers of cancer, including fragments of DNA shed by cancer cells, can show up in blood, saliva and urine. And ‘liquid biopsy’ tests, based on similar technologies to those that underpin MCED tests, are already widely used by physicians to monitor cancer progression and choose the best treatments. Detecting early-stage cancer, however, is much more difficult because of the scarcity of tumor DNA in the blood.
Some researchers say that multi-cancer tests have the potential to revolutionize cancer detection and care, especially for cancer types for which no screening tools are available. Others disagree, highlighting that the tests fail to detect many or even most early cancers, and that the downsides of false diagnoses for many people might outweigh the benefits for a few. “When you get a negative test, that’s nice, but you could still be harboring cancer,” says Eric Topol, a Physician-Researcher and Founder of the Scripps Research Translational Institute in San Diego, California. “I think it’s just irresponsible to promote these tests with the data we’ve seen so far.”
Screen time
Around one (1) in five (5) people will develop cancer during their lifetime. It is a leading cause of death in most countries, claiming some 9.7 million lives worldwide in 2022. Detecting the disease in its earlier stages usually means that treatments will be less invasive, cheaper, and more likely to result in better survival rates.
Most cancer deaths occur following late-stage diagnoses, when the disease is already advanced and has spread to other parts of the body, says Nitzan Rosenfeld, a Cancer Biotechnologist at the Barts Cancer Institute, Queen Mary University of London. “That’s because, predominantly, we rely on people noticing something unusual in their body and then going to see their physician,” he says. “The only way around that is to find cancers before they become symptomatic.”
That’s the aim of screening programs such as mammography for breast cancer; stool testing kits and colonoscopy for colorectal cancer; and smear tests for cervical cancer.
These programs are, however, far from perfect. Some people find the tests painful, embarrassing or inconvenient, so uptake varies. Screening is also unavailable for most cancer types. Preventive screening programs in the United States detect only 14% of diagnosed cancers — other screening programs or visits to the doctor do the heavy lifting.
Screening for more types of cancer using MCED tests could increase the chance of people being told they might have cancer when they do not, potentially causing anxiety and requiring invasive follow-up procedures. These risks are higher for rare cancers, for which it is harder to develop screens.
Although screening has reduced cancer deaths, researchers have, over the past three (3) decades or so, sought fresh approaches that would lower the disease burden further. The potential of MCED tests lies in their simplicity and the promise that they could catch more cancers earlier. “I think they are potentially revolutionary,” says Rosenfeld. “In the best-case scenario, if supported by trial results, they will become a standard of care.”
Clues in the blood
Established screening technologies identify specific cancer types using physiological or molecular indicators, such as signs of changes in breast-tissue density in mammograms. MCEDs have a harder task: identifying biomarkers that are linked to a range of cancers in a single blood sample.
Scientists have long known that cancers spit out bits of themselves — cells and fragments of DNA — into the blood. Many early efforts to develop blood tests for specific cancers examined these fragments for genetic mutations known to be markers of those cancers. However, because these cells and fragments from cancers are present only in low concentrations, especially in the early stages, they are masked by the huge amount of other free-floating DNA. For instance, circulating tumor DNA (ctDNA) can make up as little as 0.006% of free-floating DNA in the blood.
Improvements in the speed and accuracy of DNA sequencing have gone some way towards overcoming this challenge. In 2008, Oncologist Bert Vogelstein at Johns Hopkins University in Baltimore, Maryland, demonstrated that ctDNA could be used to detect the presence of cancer cells and therefore to predict relapse after surgery.
In 2014, Vogelstein and colleagues went on to show that they could detect ctDNA in more than 75% of people with advanced pancreatic, ovarian, colorectal, bladder, breast, and other cancers, and developed a test called CancerSEEK, which analyzed ctDNA alongside cancer proteins and was designed to pick up eight common cancer types. The technology evolved into Cancerguard, an MCED test designed to detect more than 50 types of cancer, which was launched commercially last year by Exact Sciences in Madison, Wisconsin. (In some countries, MCED tests can be marketed without Regulatory approval; however, if approved they can be more easily covered by insurance and prescribed by physicians.)
Meanwhile, the low concentrations of cancer DNA in blood have led other researchers to take different approaches. “When you’re looking for mutations in plasma, you’re looking for something that is really rare, perhaps one in a million,” says Dennis Lo, a Molecular Biologist at the Chinese University of Hong Kong.
Lo began assessing DNA fragments in the blood for epigenetic changes: marks left on the genome that turn genes on or off. His team developed a technique that can scan the entire genome for these marks — which are made by a process called DNA methylation — and showed that it could identify the locations of tumors in the body.
Grail acquired this technology in 2017 and developed a version that forms the basis of the Galleri test. Many other MCED tests are based on analyzing methylation patterns in free-floating DNA in the blood, including PanSeer, developed by Singlera Genomics in San Diego, and OverC, developed by Burning Rock in Irvine, California.
Lo and others have also used the physical appearance of tumor DNA fragments — which differ from regular DNA in various ways, including size and the structure of their ends — to reveal a cancer’s location and type.
Some research groups and companies developing MCED tests are combining multiple methods to improve accuracy. A team based at the Medical Genetics Institute in Ho Chi Minh City, Vietnam, for example, has developed SPOT-MAS, an MCED test commercially available in southeast Asia, that combines analysis of genetic mutations, methylation status, and physical properties of ctDNA to detect liver, breast, colorectal, gastric, and lung cancer.
Testing the tests
To assess whether MCEDs are ready for widespread adoption, regulators (such as the US Food and Drug Administration [FDA]), health-system leaders and insurance providers will look to trials that evaluate tests on a few measures. These include the proportion of people with cancer who have a positive result (sensitivity); the proportion of people without cancer correctly flagged as negative (specificity); and the proportion of people with a positive test result who truly have cancer (positive predictive value). This last measure depends on how common a disease is in the group being tested.
Systematic reviews pooling results from different types of studies have found that MCED tests have high specificity: they can accurately identify those without cancer in 96–99.5% of cases. Their sensitivity is more variable: they correctly catch 30–80% of those with cancer.
Many MCED tests have been evaluated only in trials in which the participants’ cancer status is already known. These trials might not be representative of wider populations. To deal with this, other studies have instead recruited people with no history of cancer and followed them over time.
One such trial evaluated the CancerSEEK blood test in women aged 65 – 75 with no history of cancer. It correctly ruled out cancer in 98.9% of people without the disease, or 99.6% when combined with a medical-imaging scan. However, it caught only 26 of the 96 cancers diagnosed during the study.
Results of a trial of the Galleri test published in 2023 followed a similar pattern. The team reported that the proportion of people without cancer who got a negative test result was 99.1% — however, of the 92 people with a positive result, only 38% were diagnosed with cancer.
In October 2025, Grail reported unpublished, preliminary results from a larger follow-up study. This evaluated Galleri’s performance in 23,000 men and women aged over 50 with no history of cancer, who had also had standard screening for breast, cervical, colorectal, and lung cancers. According to Grail, the likelihood of someone in this group with a positive test actually receiving a cancer diagnosis was 61.6%. Almost half of the time when the test result is positive, it’s actually not true,” says Anna Schuh, a Hematologist and Oncologist at the University of Oxford, UK, who is working on an MCED test that combines several detection methods to improve accuracy.
Critics also questioned some of the choices the company made about the data. The original study included more than 35,000 participants, but the results covered only a subset. In a letter to The Lancet Oncology, nine (9) researchers, including Schuh, wrote that media coverage of “hand-picked performance metrics” based on a press release demonstrated “commercially driven, premature framing of non-peer-reviewed data as proof of a transformative breakthrough”.
When contacted in February 2026, a spokesperson for Grail said that the analysis was conducted on the first 25,000 participants with one year of follow-up data, and that later this year it plans to submit the results of the full 35,000 cohort for publication.
In February 2026, they also saw the release of some top-line findings from the NHS-Galleri trial, which involves around 142,000 asymptomatic people aged 50 – 77 who also had routine screening. Participants were randomized into two (2) groups:
- one (1) had annual Galleri tests over three (3) years; and
- one (1) had blood draws and no tests.
The trial was designed to find out whether Galleri can reduce diagnosis of late-stage cancer (stages 3 and 4) by picking cases up earlier than would regular screening alone.
The trial failed to achieve statistical significance in its key objective. However, the company suggests that other trial data showed that the test has value. In people who also had standard screening, “there was a fourfold increase in the cancer detection rate among people who had annual screening with Galleri”, says Harpal Kumar, Chief Scientific Officer and President international of Grail. Kumar says that there was a “substantial” reduction in stage-4 diagnoses too, across twelve (12) cancer types that together cause two-thirds (2/3) of cancer deaths.
A spokesperson for the NHS said: “This evidence is an important step and the NHS will carefully study the full results from this major trial in the coming months.”
Challenges
Even if MCED tests are successful at detecting cancers earlier, some critics query whether this will really translate into clinical benefit. For example, a test might pick up less-dangerous cancers earlier — those that are more easily treated — and miss more-aggressive ones that kill more people. “Early detection of cancer is really important if it leads to better outcomes for patients,” says Julia Burnier, a Molecular and Cell Biologist studying liquid biopsies at McGill University in Montreal, Canada. “Whether these tests impact overall survival is a question that has not yet been answered.”
Most advocates of MCED tests, including Grail and Exact Sciences, say that the tests should complement existing screening programs, not replace them. Some public-health researchers argue that there could nonetheless be serious unintended consequences to prematurely deploying the tests widely. Tom Callender, a Public-Health Physician at the University of Cambridge, UK, and a member of the UK National Screening Committee’s multi-cancer detection tests task group, says that although current MCED tests look for a lot of cancer types, when it comes to those cancers covered by existing screening programs, they are not as sensitive. “The risk is that people think that they’ve got the all-clear, they choose not to have the established screening tests and that could lead to more preventable deaths.”
Both Grail and Exact Sciences say that, in their studies, they have seen no adverse impact of testing on adherence to standard screenings. Tom Beer, Chief Medical Officer for MCED tests at Exact Sciences, adds that such tests address an unmet need: detecting cancers with no recommended screening option.
The technologies that underpin MCED tests might have greater potential for applications other than large-scale preventive screening, some researchers say. These include helping physicians to choose the best treatment for individuals. In May 2025, the UK government announced that liquid biopsies based on ctDNA were being made available on the NHS to people in England with lung and breast cancer. The tests can confirm and characterize lung cancer more quickly than a biopsy can, and can identify people with advanced breast cancer who might benefit from targeted treatments.
They might also prove useful for screening people at high risk of cancer because of their family history, for example. “I’m confident we’re going to see more accurate tests going forward,” says Topol. “In high-risk groups, such as those with a genetic predisposition, they could be very helpful.”
One (1) area of rapid growth is applying liquid biopsies to identify whether cancer cells persist in the body after surgery or other treatment. Oncologists call this minimal residual disease testing. Several such tests are already available to physicians and many more are in development.
Callender says he is not surprised that there is a debate about the applications of multi-cancer blood tests, because the field is still in its infancy. “I don’t think we’re anywhere close to ready for widespread adoption, but it’s an exciting technology, which, if we do it properly, could be an important part of the mix in the future.”
REFERENCE: Nature; 04 MAR 2026; Nic Fleming