Every year, hundreds of thousands of people in high-income countries are diagnosed with cancers that might have been caught earlier. For some—pancreatic, ovarian, liver—there is no routine screening test at all. By the time symptoms appear, the disease has often spread. A new class of blood tests, called multi-cancer early detection (MCED), promises to change that. But despite impressive early data, no major screening guideline has adopted them. The result is a growing gap between what technology can do and what health systems will pay for.

A Single Blood Draw Detects a Dozen Cancers

The Galleri test, developed by Grail (a subsidiary of Illumina), analyzes methylation patterns on cell-free DNA that tumors shed into the bloodstream. In clinical studies, it has shown the ability to detect more than 50 types of cancer, with a reported specificity above 99%—meaning fewer than 1% of healthy people receive a false positive result. Sensitivity varies by cancer type, ranging from roughly 50% to 70% for solid tumors like lung, breast, and colorectal cancers.

For cancers that currently lack any screening—such as pancreatic, ovarian, and liver—sensitivity is lower, often below 40% in early-stage disease. But even modest detection rates could shift outcomes, because these cancers are usually diagnosed late. The test also predicts the tissue of origin with high accuracy, guiding the next diagnostic steps.

Galleri is the most advanced MCED test, but others are in development. Exact Sciences is developing a test based on DNA methylation and protein markers, while Freenome is pursuing a multi-omics approach combining cell-free DNA, RNA, and proteins. The field is moving quickly, with several tests expected to seek regulatory clearance in the next few years.

The promise is that a single annual blood draw could replace the current patchwork of organ-specific screens—mammograms, colonoscopies, Pap smears, low-dose CT scans—each with its own schedule, preparation, and adherence barriers. But that promise remains unfulfilled in clinical practice.

Guidelines Still Rely on Organ-by-Organ Screening

Today, the US Preventive Services Task Force (USPSTF) endorses only five single-cancer screening tests: mammography for breast cancer, Pap and HPV testing for cervical cancer, colonoscopy and fecal tests for colorectal cancer, low-dose CT for lung cancer in high-risk individuals, and PSA testing for prostate cancer (with shared decision-making). For pancreatic, ovarian, liver, stomach, and several other cancers, the USPSTF finds insufficient evidence to recommend routine screening.

Guideline development is deliberately slow. The USPSTF requires high-quality evidence—ideally from randomized controlled trials showing that screening reduces cancer-specific or all-cause mortality. For single-cancer screens, such trials took decades. For MCED tests, no such trial has yet reported results.

The American Cancer Society, the National Comprehensive Cancer Network, and the European Society for Medical Oncology have all issued statements acknowledging the potential of MCED but stopping short of endorsement. They cite the lack of mortality data, concerns about overdiagnosis, and uncertainty about how to manage positive results when no cancer is immediately found.

This cautious approach frustrates some oncologists and patient advocates. They argue that the specificity data are strong, that stage shift (detecting cancers earlier) is a reasonable surrogate, and that waiting for mortality results means delaying access for patients who could benefit now. But guideline panels must weigh these arguments against the risk of widespread false positives, unnecessary procedures, and health system costs.

The Evidence Gap That Keeps MCED Out of Clinics

The core debate centers on what counts as proof. Grail and its supporters point to a large case-control study published in the Journal of Clinical Oncology, which showed that Galleri detected 51.5% of cancers across stages, with a false-positive rate of 0.5%. When a cancer signal was detected, the test correctly predicted the tissue of origin in 88.7% of cases.

But case-control studies are vulnerable to bias. The gold standard is a randomized controlled trial (RCT) in which asymptomatic people are assigned to receive the test or not, and then followed for years to see if cancer mortality decreases. The NHS-Galleri trial, launched in 2021, is exactly that: it is recruiting 140,000 participants in England, randomly assigning them to receive Galleri or standard care. Results are expected around 2026.

Critics note that even if the trial shows a reduction in late-stage diagnoses—a so-called stage shift—it may not translate into a mortality benefit. Lead-time bias can make survival appear longer without actually changing the course of disease. Overdiagnosis, where a test finds a cancer that would never have caused symptoms, is another concern. For some cancers, especially prostate and thyroid, overdiagnosis is well documented.

A smaller but important issue is what happens after a positive test. In Grail's studies, about 1% of participants received a positive result, and of those, roughly 40% were eventually diagnosed with cancer. The remaining 60% underwent further testing—often including PET scans, endoscopies, and biopsies—without a cancer diagnosis. These false positives cause anxiety and carry risks from invasive procedures. The question is whether the benefits of earlier detection outweigh these harms.

To put this in perspective, consider the experience of a hypothetical 60-year-old woman with no symptoms. She hears about the test, pays out of pocket, and receives a positive result. She then undergoes a whole-body PET scan, which reveals a small nodule in her pancreas. A biopsy confirms early-stage pancreatic cancer—a disease with a five-year survival rate of roughly 10% when diagnosed after symptoms, but around 40% when caught at stage I. In this scenario, the test could be life-saving. But another 60-year-old with the same positive result might undergo the same workup only to find no cancer after multiple biopsies, leaving her with anxiety and a small risk of complications from the procedures. The balance of benefit and harm is personal, and guidelines struggle to capture that nuance.

Who Pays When Insurance Says No

Grail sells Galleri as a laboratory-developed test, which means it does not require FDA premarket approval. The list price is roughly US$ 949 per test. Medicare and most private insurers currently do not cover it for asymptomatic individuals. A few private plans have begun offering coverage under certain conditions, but widespread reimbursement remains elusive.

For patients who want the test, the cost is almost entirely out-of-pocket. Some employers have added Galleri to their workplace wellness programs, covering the test for employees. But this creates disparities: a tech worker in Silicon Valley may have access, while a teacher in rural Ohio likely does not. A recent survey by the American Cancer Society found that nearly 30% of adults aged 50–79 said they would be interested in an MCED test if it were covered by insurance, but only about 5% would pay US$ 1,000 out of pocket. Cost sensitivity is a major barrier to uptake.

Insurance companies are waiting for guideline inclusion. Without a recommendation from the USPSTF or a similar body, they have little incentive to pay. The US Centers for Medicare & Medicaid Services (CMS) has not issued a national coverage determination for MCED tests, leaving decisions to local contractors, who have generally denied coverage. Some contractors have cited the lack of evidence that the test improves health outcomes, a standard that may be met only after the NHS-Galleri trial reports.

The cost could come down with competition and scale. Exact Sciences and Freenome have not announced pricing for their tests, but analysts expect a range of US$ 500 to US$ 1,000. Even at the lower end, that is more than most single-cancer screens. But proponents argue that the cost is justified if it reduces late-stage diagnoses and expensive treatments. A health-economic analysis funded by Grail suggested that Galleri could be cost-effective if priced around US$ 500 and used in adults aged 50 and older. However, independent analyses have been more cautious, noting that the downstream costs of follow-up tests and procedures could offset savings from earlier detection.

Early Adopters and the Risk of Hype

Despite the lack of guidelines, Galleri is already being marketed directly to consumers and through healthcare providers. Grail has partnerships with several large health systems, including Intermountain Healthcare and Providence, to offer the test in clinical settings. Oncologists report that patients sometimes ask for the test, having heard about it through news coverage or social media.

Professional societies have urged caution. The American Society of Clinical Oncology (ASCO) has not endorsed MCED for routine use, and the European Society for Medical Oncology (ESMO) notes that the evidence is insufficient to recommend screening in asymptomatic individuals. Some experts worry that direct-to-consumer marketing will lead to inappropriate use, with people who are not at average risk seeking the test and facing unnecessary follow-up.

There is also the risk of overdiagnosis, particularly for cancers that are slow-growing or indolent. For example, some thyroid and prostate cancers detected by MCED might never cause harm, but once found, they are likely to be treated aggressively. The balance of benefits and harms may vary by age and comorbidity. For an 80-year-old with heart disease, finding a small prostate cancer may lead to treatment that causes more harm than the cancer itself. Yet the MCED test cannot distinguish between aggressive and indolent cancers—it only signals the presence of a tumor.

Patient advocates counter that informed adults should have the right to access the test if they understand the limitations. Shared decision-making, they argue, can help individuals weigh the potential benefits against the known harms. But this places a burden on primary care clinicians, who may not have the time or training to explain the nuances of MCED. A typical primary care visit lasts 15–20 minutes, and adding a discussion about a test with a 1% positive rate and a 40% cancer confirmation rate is not straightforward. Some clinics have developed decision aids, but their use is not widespread.

Regulators Move Faster Than Guidelines

The US Food and Drug Administration (FDA) has not approved Galleri for screening, but it has granted the test Breakthrough Device designation, which is meant to expedite development and review. Because Galleri is offered as a laboratory-developed test, it can be marketed without FDA clearance, though the agency has signaled that it intends to increase oversight of such tests. In 2023, the FDA issued draft guidance on the development of MCED tests, outlining expectations for clinical studies. The agency emphasized the need for randomized trials with mortality endpoints, though it acknowledged that other study designs might be acceptable in some circumstances. The final guidance, expected in 2025, could shape the future of the field.

In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) has not yet approved any MCED test for screening. The NHS-Galleri trial is being conducted under special arrangements, with participants receiving the test as part of a research study. If the trial shows positive results, the National Screening Committee would then evaluate whether to recommend Galleri for routine use—a process that could take years. The UK has a centralized screening system, which could facilitate rapid implementation if the evidence supports it, but also means that adoption is all-or-nothing.

In Europe, Grail has not sought CE marking for Galleri, which would be required for marketing in EU countries. The company has said it is focused on the US and UK markets first. Other MCED developers may pursue European approval sooner, potentially creating a patchwork of availability. For example, a test developed by a European company might launch in Germany or France before Galleri reaches those markets, leading to different levels of access across the continent.

Regulatory pathways also differ for tests that combine multiple biomarkers. Freenome's multi-omics approach, for instance, might face different scrutiny than a methylation-only test. The FDA has not yet issued test-specific guidance for such platforms, leaving developers to navigate uncertain requirements. This regulatory ambiguity can delay investment and slow the pace of innovation.

What the Next Five Years Will Decide

The NHS-Galleri trial is the most anticipated study in cancer screening. If it shows a reduction in cancer mortality, it could transform guidelines and reimbursement almost overnight. If it does not, the field may need to reconsider its approach. Other trials are also underway: the PATHFINDER study in the US is evaluating the clinical utility of Galleri in a real-world setting, and the STRIVE study is collecting longitudinal data. Together, these studies will provide a more complete picture of the test's performance and impact.

Even if the results are positive, implementation challenges remain. Health systems will need to decide who to screen, how often, and what follow-up protocols to use. The capacity for diagnostic workups—imaging, endoscopy, biopsy—may be strained if millions of people begin receiving positive test results. A modeling study from the UK estimated that if the NHS-Galleri trial leads to national screening, the demand for PET scans could increase by roughly 20–30%, requiring additional investment in equipment and personnel. Similarly, the number of referrals to cancer specialists could double, potentially overwhelming existing services.

And there is the question of equity: will MCED widen or narrow existing disparities in cancer outcomes? Early adopters tend to be wealthier and more educated, which could exacerbate gaps. But if insurers eventually cover the test, and if it is offered in community health centers, it might reach populations that currently have low screening rates for colorectal, breast, and cervical cancers. For example, Black Americans have higher mortality rates from several cancers, partly due to later diagnosis. An MCED test that is accessible and affordable could help close that gap, but only if it is deployed equitably.

Competing tests are also advancing. Exact Sciences has announced plans to launch its own MCED test by 2026, and Freenome is recruiting for a large clinical trial. As more tests enter the market, prices may fall, but the evidence base will need to be compared. It is possible that different tests will perform better for different cancer types, leading to a future where clinicians choose among several options. Head-to-head trials, though expensive, may become necessary to guide choices. Some researchers have called for a "publicly funded" comparison platform, similar to the UK's National Institute for Health and Care Excellence (NICE) technology appraisals, to evaluate MCED tests systematically.

For now, the most likely near-term scenario is that MCED tests become available through shared decision-making, with insurers covering them only for high-risk individuals or as part of research. Guideline bodies are preparing for this: the USPSTF has published a research agenda that includes MCED, and the International Agency for Research on Cancer has convened working groups. But until the mortality data arrive, the gap between what is possible and what is recommended will persist.

This article is for informational purposes only and does not constitute medical advice. Individuals considering cancer screening should consult their healthcare provider.