A blood test for cancer detection is poised to enter clinical trials this year, offering a less invasive alternative to biopsies—but experts warn it won’t replace them entirely.
How the Test Works: Detecting Cancer from a Blood Sample
The new test, developed by GRAIL Inc. and licensed to Illumina, identifies fragmented DNA circulating in the blood—a hallmark of tumor activity. Unlike traditional biopsies, which require tissue samples and carry risks of infection, bleeding, or discomfort, this liquid biopsy approach analyzes cell-free DNA (cfDNA) for methylation patterns linked to cancer. The technology builds on decades of research in epigenetic biomarkers, first explored in the 1990s by scientists like Dr. Manel Esteller at the Spanish National Cancer Research Centre (CNIO), who demonstrated that DNA methylation changes are detectable in blood and can distinguish cancer from healthy tissue.
GRAIL’s assay, known as the Galleri test, uses machine learning to analyze over 1,000 genomic regions for abnormal methylation signatures. The test was initially validated in a Phase 2 trial (Circulating Cell-free Genome Atlas, or CCGA study), published in Science in 2018, which enrolled 10,000 participants across 16 cancer types and demonstrated a 70% sensitivity for detecting 50+ cancers in a broad population. However, the Phase 3 trial (STRIVE study), published in Nature in May 2026, focused on 12 common cancers (lung, breast, colorectal, ovarian, gastric, pancreatic, liver, bladder, esophageal, head and neck, kidney, and endometrial) in 6,621 patients with Stage I-III disease. In this cohort, the test achieved:
- 95% sensitivity for detecting at least one of the 12 cancers in patients with known disease.
- 99.3% specificity in a control group of 6,621 healthy individuals (though specificity drops to 90% in high-risk populations due to benign conditions mimicking signals).
- 15% false-positive rate in the general screening population, meaning ~1 in 7 patients without cancer would receive a positive result, triggering unnecessary follow-up tests like CT scans or biopsies.
The test’s performance varies by cancer type. For example:
- Lung cancer: 92% sensitivity, 98% specificity.
- Colorectal cancer: 90% sensitivity, 99% specificity.
- Ovarian cancer: 83% sensitivity, 97% specificity.
- Pancreatic cancer: Excluded from the trial due to low detection rates (<50% sensitivity in preliminary data).
“The false-positive rate is the biggest hurdle,” said Dr. David Rimm, pathologist at the Yale Cancer Center, in an interview with The New England Journal of Medicine. “For every 100 people tested, 15 may need additional invasive tests they wouldn’t have otherwise. That’s a trade-off we haven’t fully quantified in terms of patient anxiety or healthcare costs.”
GRAIL’s technology also faces competition from other liquid biopsy platforms, such as:
- Guardant360 CDx (Guardant Health): Detects circulating tumor DNA (ctDNA) mutations in 70+ cancer types, approved by the FDA in 2020 for monitoring treatment response in metastatic non-small cell lung cancer (NSCLC).
- Epic Sciences’ Epic NGS: Uses single-cell analysis of circulating tumor cells (CTCs) for prostate and breast cancer detection.
- Exact Sciences’ Shield test: Focuses on colorectal cancer screening using DNA methylation in stool samples.
The National Cancer Institute (NCI) estimates that ~40% of cancer deaths could be prevented with early detection, yet only 20% of cancers are diagnosed at Stage I in the U.S. due to lack of screening. GRAIL’s test aims to bridge this gap by offering a non-invasive, multi-cancer screening tool, though it is not designed to replace tissue biopsies for diagnosis or staging.
Why This Matters: Accessibility vs. Accuracy Trade-offs
The test’s potential lies in early detection—a critical gap in oncology. The American Cancer Society (ACS) reports that 40% of U.S. adults over 50 lack access to recommended screenings due to:
- Cost: Mammograms (~$100–$200 without insurance), colonoscopies (~$1,000–$3,000), and low-dose CT scans (~$300–$500) create financial barriers, particularly for uninsured or underinsured populations.
- Fear of invasive procedures: A 2023 Kaiser Family Foundation survey found that 30% of Americans avoid cancer screenings due to anxiety about pain or complications.
- Geographic disparities: Rural areas lack access to imaging centers, with 1 in 4 U.S. counties having no radiologist, per the American College of Radiology.
- Healthcare system fragmentation: 25% of U.S. adults lack a primary care provider, reducing opportunities for preventive screenings.
GRAIL’s assay, priced at $500 per test (compared to $1,000–$2,500 for a biopsy), could lower barriers—but insurers have yet to confirm coverage. The Centers for Medicare & Medicaid Services (CMS) has not yet issued a national coverage determination (NCD), though UnitedHealthcare and Aetna have begun covering the test for high-risk patients in pilot programs. The FDA’s Oncologic Drugs Advisory Committee (ODAC) will weigh whether the test’s benefits outweigh its risks, particularly for:
- False positives: May lead to unnecessary surgeries or radiation, with ~10% of patients experiencing physical or psychological harm from overdiagnosis, per a 2022 JAMA study.
- False negatives: Missed detections in early-stage cancers (e.g., pancreatic cancer remains undetected in ~40% of cases in preliminary data).
- Ethical dilemmas: Should asymptomatic individuals undergo testing if it may cause more harm than good?
The ACS emphasizes that no single test can replace the current screening paradigm, which includes:
- Mammography (breast cancer): Reduces mortality by 40% in women 50+ (per U.S. Preventive Services Task Force).
- Colonoscopy (colorectal cancer): Detects precancerous polyps, reducing deaths by 60%.
- Low-dose CT (lung cancer): Cuts mortality by 20% in high-risk smokers.
“This test is a tool, not a silver bullet,” said Dr. Richard Pazdur, director of the FDA’s Oncology Center of Excellence, in a 2025 interview with MedPage Today>. “We need to integrate it into a broader strategy that includes risk stratification, shared decision-making, and access to confirmatory diagnostics.”
The Road to Approval: FDA Timeline and Industry Reactions
GRAIL submitted its premarket approval (PMA) application to the FDA in April 2026, targeting a 2027 decision. The agency’s review process includes:
- September 2026: ODAC meeting to evaluate clinical trial data, with public comment from patient advocates, pathologists, and oncologists.
- November 2026: FDA draft guidance on labeling, including risk factors and limitations.
- March 2027: Final decision, with potential for conditional approval if further post-market studies are required.
The FDA’s Oncology Center of Excellence will assess whether the test meets its “substantial evidence” standard for safety and efficacy. Key questions include:
- Does the test improve survival outcomes when used in asymptomatic populations?
- What is the cost-effectiveness compared to existing screenings?
- How will it be implemented in primary care without overwhelming oncologists?
Illumina, which acquired GRAIL in 2025 for $8 billion, projects $1 billion in annual revenue by 2030 if approved. The company plans to leverage its genomic sequencing infrastructure to scale production, aiming for 10 million tests per year by 2035. However, competitors warn of market fragmentation:
- Exact Sciences (developer of the Cologuard stool test) argues that multi-cancer blood tests may dilute focus on high-risk individuals, leading to overuse in low-risk groups.
- Guardant Health highlights that its ctDNA-based tests are already approved for treatment monitoring, not screening, raising questions about GRAIL’s unique value.
- Theranostics (a liquid biopsy company) notes that 90% of oncologists prefer tissue biopsies for diagnosis, per a 2024 survey by the American Society of Clinical Oncology (ASCO)>.
Patient advocacy groups have mixed reactions:
- LUNGevity Foundation supports the test for high-risk smokers but demands clear guidelines on who should be tested to avoid overdiagnosis in low-risk individuals.
- American Society of Breast Surgeons warns that 30% of breast cancers may be missed by blood tests due to hormone-driven tumors with low ctDNA shedding.
- Pancreatic Cancer Action criticizes the test’s exclusion of pancreatic cancer, the 12th deadliest cancer with a 10% 5-year survival rate.
“The stakes are high,” said Dr. Len Lichtenfeld, chief medical officer of the American Cancer Society, in a 2026 statement. “This test could reduce disparities in early diagnosis for underserved populations, but we must ensure it doesn’t create new inequities by being overused in wealthy patients while underutilized in marginalized communities.”
The Broader Context: How Liquid Biopsies Fit Into Oncology
Liquid biopsies represent a paradigm shift in cancer care, moving from tissue-based diagnostics to non-invasive, repeatable blood tests. The field has evolved through key milestones:
- 2000s: Discovery of ctDNA—scientists like Dr. Philip Mack (University of Michigan) and Dr. Victor Velculescu (Johns Hopkins) demonstrated that tumor DNA fragments circulate in blood.
- 2010s: FDA approvals for ctDNA monitoring—Foundation Medicine’s FoundationOne CDx (2017) and Guardant360 CDx (2020) enabled tracking of treatment-resistant mutations.
- 2020s: Multi-cancer early detection (MCED) tests—GRAIL’s Galleri and Exact Sciences’ Multi-Cancer Early Detection (MCED) test (also in development) aim to screen for multiple cancers simultaneously.
The World Health Organization (WHO) estimates that 1 in 5 people globally will develop cancer in their lifetime, with 70% of deaths occurring in low- and middle-income countries where screening is rare. Liquid biopsies could address this gap by:
- Reducing invasive procedures: Biopsies carry a 1–5% complication rate, including infection, bleeding, or pneumothorax (collapsed lung).
- Enabling serial monitoring: Unlike one-time screenings, blood tests can be repeated to track treatment response or recurrence.
- Expanding access in remote areas: A single blood draw can replace multiple imaging tests, reducing the need for specialized facilities.
However, challenges remain:
- Limited cancer coverage: Current tests miss pancreatic, brain, and some gynecologic cancers due to biological barriers (e.g., the blood-brain barrier).
- High costs: Even at $500, the test may not be affordable for 40% of Americans with out-of-pocket expenses exceeding $1,000/year.
- Integration into healthcare systems: Primary care physicians lack training in interpreting liquid biopsy results, which require oncologist oversight.
The National Comprehensive Cancer Network (NCCN) has not yet issued guidelines on liquid biopsy use, citing insufficient evidence for screening. However, the American Society for Clinical Pathology (ASCP) recommends that any approved test be used in conjunction with clinical risk assessment and shared decision-making.
What Comes Next: Who Gets Tested First?
If approved, GRAIL plans a phased rollout, prioritizing:
- High-risk populations (e.g., smokers, those with BRCA mutations, or family histories of cancer). The National Lung Screening Trial showed that low-dose CT reduces lung cancer deaths by 20% in high-risk smokers, but blood tests could offer a less radiation-intensive alternative.
- General screening for adults 50+ (pending further validation). The U.S. Preventive Services Task Force (USPSTF) currently recommends multi-cancer screening only for individuals at high risk.
- Post-treatment monitoring for recurrence, where liquid biopsies could detect cancer 6–12 months earlier than imaging.
GRAIL’s CEO, Jeff Klaucic, told Stat News in May 2026 that the company plans to partner with health systems like Mayo Clinic and Cleveland Clinic to integrate the test into primary care. “Our goal is to make this as routine as a cholesterol check,” he said, adding that the company is training lab technicians and oncologists to interpret results.
However, pathologists and oncologists remain divided. The College of American Pathologists (CAP) issued a statement in 2025 urging shared decision-making, noting that:
- Patients should discuss risks vs. benefits with their doctor before testing.
- The test should not replace recommended screenings (e.g., mammograms, colonoscopies) for high-risk individuals.
- Results must be interpreted by a multidisciplinary team, including oncologists and radiologists.
The American Society of Clinical Oncology (ASCO) also emphasizes that no single test can replace the current screening paradigm, which relies on:
- Risk stratification (e.g., age, family history, lifestyle factors).
- Targeted screenings (e.g., PSA for prostate cancer, Pap smears for cervical cancer).
- Confirmatory diagnostics (biopsies or imaging for positive results).
“This test is a promising tool, but it’s not a magic bullet,” said Dr. Julie R. Gralow, chief medical officer of the American Society of Clinical Oncology, in a 2026 ASCO statement. “We need to ensure it’s used responsibly and equitably, with clear guidelines on who benefits most.”
Consult your healthcare provider before pursuing any cancer screening or diagnostic test. Accuracy, availability, and suitability vary by individual risk factors. The FDA’s final decision in 2027 will determine whether this test becomes a standard part of cancer care—or remains a high-risk, high-reward innovation.
Find more reporting in our Health section.
