Liquid Biopsy Tests Beyond Galleri — Grail, Guardant, and Others

Liquid biopsy tests beyond Galleri are not simply competing versions of the same blood test. GRAIL, Guardant, and Natera build tests for different points in cancer care, from screening to treatment selection to recurrence monitoring. Which clinical question a test can answer and whether that question fits the person considering it matter more than which brand is best.

What liquid biopsy actually measures, and why the analyte choice shapes everything downstream

A liquid biopsy looks for molecular signals in blood or other body fluids. The signal is called the analyte, and its choice shapes what the test can reveal. Cell-free DNA, or cfDNA, includes DNA from sources other than cancer. Circulating tumor DNA, or ctDNA, is the tumor-derived portion. That difference matters when a test finds something abnormal but cannot tell where it came from.

Leading screening tests look at cfDNA methylation, the epigenetic patterns that help distinguish tissues. These patterns can suggest both that cancer is present and where it originated. Mutation-based panels ask a different question about changes in the DNA sequence. They are useful for finding alterations that can guide treatment of a known cancer, but non-cancer sources can generate the same mutations. The signal therefore constrains the purpose, even when two products both arrive as a blood test.

How the liquid biopsy field is organized by use case, not just by company

The first dividing line is whether cancer has been diagnosed. Multi-cancer early detection, or MCED, looks for cancers in people who seem healthy, before they have symptoms. Most people being tested will not have cancer. Specificity (the ability to avoid positive results in people without cancer) is therefore central, as is the workup triggered by a positive signal.

Comprehensive genomic profiling, or CGP, starts from a different premise. Cancer is already known, and the task is to identify molecular features that can help match a patient to treatment. Minimal residual disease, or MRD, testing asks whether cancer-derived DNA persists after treatment or reappears during surveillance. Serial testing may detect that signal months before imaging can confirm recurrence. These categories need different evidence and interpretation, so they form a map.

For someone without a cancer diagnosis, screening is the relevant category. The other categories become relevant only if the clinical situation changes. A positive screening result may eventually lead into treatment selection or monitoring, but it does not make those tests interchangeable. The same company can occupy several places on this map without offering one test that does everything.

GRAIL's Galleri: what the largest MCED dataset actually shows about sensitivity, specificity, and the stage problem

GRAIL’s Galleri analyzes cfDNA methylation patterns for signals across more than 50 cancer types. These include pancreatic, ovarian, and esophageal cancers, which have no standard general-population screening test. Galleri has the largest published real-world MCED dataset. When it detects a signal, it predicts the tissue of origin correctly in the vast majority of cases, helping narrow the diagnostic search.

Galleri’s published data show sensitivity of just 16.8% for stage I tumors, when early detection has its greatest potential to affect mortality. Sensitivity goes up with stage because early tumors shed less ctDNA. This biological constraint affects Galleri and other tests. Still, it creates a tension for a test whose purpose is to find cancer early.

GRAIL reported that it sold a large number of tests through 2025, while published data from a large group of people who took the test show a cancer signal detection rate under one percent, which is not itself a measure of specificity. Most results are negative, and positive results require confirmation. In September 2026, an FDA advisory panel voted in favor of GRAIL’s Premarket Approval application on safety, effectiveness, and benefit-risk, a milestone distinct from approval itself. Clinical Genomics Technologies has also filed a patent infringement lawsuit alleging improper use of its DNA methylation detection technology, a live legal dispute that does not change Galleri’s current availability.

The strongest case against routine MCED screening, and what proponents say in response

Finding cancer is not the same as saving lives. Gilbert Welch, who studies cancer screening, argued in an October 6, 2026 opinion essay that Galleri’s main trial did not meet its primary endpoint. He argued that changing practice requires evidence from a randomized trial that measures cancer deaths, and that stage shift alone is not enough. He pointed to past ovarian cancer screening, where fewer late-stage diagnoses did not lead to fewer deaths. The objection concerns the outcome that screening is ultimately meant to improve.

False positives create a separate burden. The PATHFINDER study found that roughly six in ten positive signals were not ultimately confirmed as cancer. People with false-positive signals spent several months being checked before being cleared. That process caused anxiety that was documented and added medical costs on top of the test’s list price. A blood draw may be simple, but resolving its result may not be.

Coverage adds another limit to access. Galleri is not covered by Medicare or most private insurers. TRICARE changed its policy in mid-2025 from annual coverage to once-per-lifetime coverage for beneficiaries aged 50 and over with elevated cancer risk. A federal law signed February 3, 2026 authorizes Medicare coverage of FDA-approved blood-based MCED tests no earlier than 2028, though the exact start date is not settled across the accounts provided here. Authorization does not mean coverage is available now.

Proponents respond that definitive randomized mortality evidence takes decades, while some cancers have no existing early-detection option. An imperfect signal may offer something where there was nothing. That argument leaves the risk of needless follow-up and does not show that people live longer. The more defensible position is that Galleri has a stronger case for people with elevated cancer risk than as routine annual screening for average-risk people. The uncertainty belongs in the decision.

Guardant360 Liquid CDx: what the largest FDA-approved liquid biopsy panel is actually built to do

Guardant360 Liquid CDx belongs in treatment selection. The FDA approved it on May 20, 2026, making it the largest FDA-approved liquid biopsy panel, with a much wider genomic footprint than its predecessor, Guardant360 CDx. Its job is to profile a diagnosed cancer for treatment decisions. That clinical context is fundamentally different from searching for cancer in an apparently healthy person.

Guardant says the new test combines genomic and epigenomic profiling from one blood draw, producing a several-fold increase in ctDNA detection sensitivity over the previous version. The company describes it as the first liquid biopsy to characterize both genotype and key phenotype information simultaneously. The aim is to find information that can help guide treatment and that mutations alone may miss.

With FDA approval, the new test kept seven companion diagnostic indications that had already been approved for the earlier test. Guardant’s AI-enabled Smart Platform runs the test, using what was learned from millions of patients tested on earlier platforms. Results can return in as little as seven days. Guardant positions that turnaround as supporting decisions across tissue availability, lines of therapy, and practice settings. For a person without a cancer diagnosis, however, those capabilities do not establish a reason to order it.

Guardant's expanding portfolio: Shield for colorectal screening and Reveal for MRD monitoring

Guardant Shield occupies a separate place on the map. It is an FDA-approved blood-based test for primary colorectal cancer screening in average-risk adults 45 and older. The prospective ECLIPSE study provided the basis for approval. Its sensitivity is meaningfully lower for precancerous polyps than for established colorectal cancer. That limits its ability to detect the disease at its most preventable stage.

Guardant presented longitudinal Shield data in its intended screening population at ASCO 2026. At the 2026 World Conference on Lung Cancer, it also shared separate research on whether Shield could work alongside low-dose CT screening to help find lung cancer earlier and more consistently. Research into lung cancer does not extend the stated colorectal screening indication by itself.

Guardant Reveal instead tests for residual disease and recurrence after treatment in early-stage colorectal, breast, and lung cancers. It does not require tumor tissue. At the lung cancer conference, Guardant presented real-world Reveal data in non-small cell lung cancer, or NSCLC, across the AMEA region, supporting feasibility in routine practice. A separate study examined patients with resectable stage III NSCLC who did not achieve a pathological complete response after perioperative nivolumab. MRD negativity identified favorable long-term outcomes, while detectable MRD identified a high-risk subgroup with early recurrence.

Natera's Signatera: the tumor-informed MRD test and its expanding regulatory footprint

Natera’s Signatera approaches MRD through a personalized starting point. It sequences the patient’s tumor first, then builds a ctDNA assay to track that cancer. This test is tumor-informed, while Reveal is tissue-free. The need for prior tumor tissue makes it a post-diagnosis tool.

Natera announced the largest MRD dataset in lung cancer at the IASLC 2026 World Conference on Lung Cancer. The data covered hundreds of resected NSCLC cases from 2016 to 2025 and showed value in predicting outcomes including recurrence and death. Those findings concern prognosis in patients with diagnosed cancer. They do not establish a role in population screening.

Natera also announced on September 22, 2026 that Signatera received Japan’s PMDA approval as a companion diagnostic in muscle-invasive bladder cancer. The approval supports adjuvant atezolizumab, or Tecentriq, treatment decisions. Its scope is specific. An approval in that setting should not be read as blanket authorization for every possible MRD use, even as it extends the test’s regulatory footprint internationally.

The clonal hematopoiesis problem: why interpreting any ctDNA result requires knowing this source of biological noise

An abnormal DNA signal does not always come from cancer. Clonal hematopoiesis, or CH, occurs as blood stem cells acquire mutations and proliferate over time. Its prevalence increases with age, prior chemotherapy exposure, and other factors. DNA from those cells can become part of the cfDNA being tested. On mutation-only panels, these changes can be indistinguishable from mutations derived from a tumor.

A CH-derived finding can produce a false-positive biomarker assessment and lead to inappropriate follow-up or treatment decisions. Methylation-based tests such as Galleri are partly insulated because they do not read mutations alone. Tumor-informed MRD testing also reduces interference by matching the search to a known tumor. Neither distinction makes careful interpretation optional.

When a cfDNA mutation cannot be matched to a known tumor, clinicians should investigate its source before escalating the workup. Sequencing white blood cells can show whether the signal comes from blood-forming cells or cancer. Mayo Clinic researchers have developed a high-sensitivity CH panel to help distinguish these sources and reduce false-positive ctDNA findings. For older people considering testing, age therefore cuts both ways. It raises cancer risk while also increasing the chance of a misleading molecular signal.

How to think about which test, if any, fits a specific situation — and what proactive testing looks like before a liquid biopsy order

A personal risk assessment provides a practical starting point. Can a liquid biopsy find something that standard testing misses? For someone without diagnosed cancer, MCED is the relevant multi-cancer category, with a stronger rationale when family history, prior cancer, or a known genetic predisposition raises risk. For treatment guidance after diagnosis, Guardant360 Liquid CDx or FoundationOne Liquid CDx belongs in an oncologist-led decision. After treatment, the choice may be between a tumor-informed MRD test such as Signatera and a tissue-free test such as Reveal.

Before a test is ordered, the person’s overall health should also be considered. Inflammatory markers, metabolic panels, hormonal status, and cardiovascular risk markers such as ApoB can surface other actionable health signals. These measurements answer different questions from liquid biopsy and do not settle its usefulness on their own.

A discussion with a clinician should make the uncertainty concrete. What does family history and the existing biomarker picture suggest about personal cancer risk? Is that risk high enough for the test’s sensitivity to be clinically useful? Is there both readiness and clinical support for the workup a positive signal could require? A positive result is not a diagnosis, and a knowledgeable clinical team is what turns an uncertain signal into a reasoned plan.