Guardant Health, a California company, makes several blood tests that read circulating tumor DNA, the fragments of DNA that cancers release into the blood. The tests answer different questions, and the names are easy to confuse. Guardant360 reads the genes of an advanced cancer from a blood draw to find treatment targets. Guardant Reveal looks for cancer left behind after treatment without needing tumor tissue. Shield is a screening test for colorectal cancer in people who have not been diagnosed. This article explains what each test does, the 2026 FDA approval, the research from Japan, and the limits of each.
Cancer Expert MD has no financial relationship with Guardant Health or any other laboratory and receives nothing for referrals.
Guardant360: Finding Treatment Targets From a Blood Draw
For advanced cancer, Guardant360 looks for the mutations that targeted drugs act on, such as changes in EGFR, ALK, KRAS, BRAF, HER2 and ESR1. In May 2026 the FDA approved Guardant360 Liquid CDx, a newer version that reads both genetic mutations and epigenetic changes, the chemical tags that switch genes on and off. According to the company, it covers a far wider portion of the genome than the earlier test and detects tumor DNA several times more sensitively. It is approved as a companion diagnostic for targeted drugs in lung, colorectal and breast cancer, and results can come back in about a week.1
Why blood instead of tissue. A blood test avoids a new biopsy, comes back faster, and picks up DNA shed from every tumor site in the body. That makes it especially useful for finding the new resistance mutations that can appear when a targeted drug stops working. Our article on what to do when chemotherapy stops working explains why re-testing the cancer as it is now matters.
Its limits. When very little tumor DNA is in the blood, a negative result does not rule out a mutation, and tissue testing is still needed. The blood can also carry mutations from aging blood cells rather than from the cancer, which must be recognized when reading the report. Guardant also offers a tissue test that now includes whole transcriptome profiling, reading the cancer’s RNA as well as its DNA; our article on tumor DNA and RNA sequencing explains why that matters.
Research From Japan: Faster Testing, More Patients in Trials
In Japan’s nationwide SCRUM-Japan program, researchers compared blood testing with Guardant360 against tissue testing in people with advanced gastrointestinal cancers. Blood testing returned results in a median of 11 days compared with 33 days for tissue, and more than twice as many patients enrolled in matched clinical trials, 9.5 percent compared with 4.1 percent, with no loss of treatment benefit.2
Guardant Reveal: Looking for Cancer Left Behind Without Tissue
Guardant Reveal looks for tumor DNA in the blood after surgery or treatment, but unlike Signatera it needs no tumor tissue. Instead of tracking a patient’s own mutations, it reads cancer-related patterns of chemical tags on DNA in the blood. It is used in early-stage colorectal, breast and lung cancer, and since late 2025 it has also been offered to track how well treatment is working in advanced cancer.3
Tissue-free or tumor-informed? Tumor-informed tests such as Signatera are generally regarded as more sensitive at the very lowest levels of tumor DNA. Tissue-free tests can be used when no tumor sample is available and give a first result sooner. The right choice depends on the cancer and on whether tissue exists.
Shield: A Blood Test for Colorectal Cancer Screening
Shield is the first blood test approved by the FDA as a primary screening option for colorectal cancer, for adults 45 and older at average risk. Medicare covers it, and it is included in the colorectal cancer screening guidelines of the National Comprehensive Cancer Network and the American Cancer Society.3
In the ECLIPSE study of about 8,000 adults, published in the New England Journal of Medicine in 2024, Shield detected 83 percent of colorectal cancers but only 13 percent of advanced precancerous polyps.4 Colonoscopy finds and removes those polyps at the same visit, so it remains the most complete screening test. Shield is a good option for people who will not have a colonoscopy, and a positive result must be followed by one. Guardant is also developing a multi-cancer version of Shield; our article on multi-cancer early detection blood tests explains what these tests can and cannot do.
Which Guardant Test Answers Which Question
Advanced cancer, looking for treatment targets: Guardant360 Liquid, or the tissue version when a sample is available.
After surgery for early-stage cancer, looking for cancer left behind: Guardant Reveal, or a tumor-informed test such as Signatera.
Advanced cancer, tracking whether treatment is working: Guardant Reveal therapy monitoring.
No cancer diagnosis, colorectal cancer screening at average risk: Shield, with colonoscopy for any positive result.
Guardant360 is covered by Medicare for advanced solid tumors and by many private insurers, and Medicare coverage for Guardant Reveal has expanded. Coverage changes often, so it is worth checking before testing. In a consultation, Dr. Silver, MD, educates you on which blood tests apply to your type and stage of cancer and what each result can and cannot tell you.
How Cancer Expert MD Helps
Cancer Expert MD provides education and consultation for people with every type and stage of cancer, and specializes in Stage IV and metastatic cancer. Our book, The New Reality of Cancer, explains how to combine blood tests, tumor sequencing and imaging into one monitoring plan. See also our advanced cancer testing guide.
Frequently Asked Questions
What is Guardant360 used for?
To find mutations in an advanced cancer that targeted drugs act on, using a blood draw instead of a biopsy.
Is Guardant360 as accurate as a tissue biopsy?
When enough tumor DNA is in the blood, it finds the main targetable mutations reliably and quickly. When little tumor DNA is present it can miss them, so a negative result is often followed by tissue testing.
What is the difference between Guardant Reveal and Signatera?
Signatera is built from the patient’s own tumor and tracks that cancer’s mutations. Guardant Reveal needs no tissue and reads cancer-related patterns in the blood instead.
Can the Shield blood test replace a colonoscopy?
It is an approved screening option for people who will not have a colonoscopy, but it finds far fewer precancerous polyps, and a positive result requires a colonoscopy.
About the author. Dr. Silver, MD, graduated from Temple University School of Medicine, completed fellowship training in cardiology, and has practiced medicine for nearly fifty years. A lymphoma survivor of about twenty-five years, he is co-author, with Dr. Lindmeier, DHSc, of The New Reality of Cancer: The Science of Recovery. Read more about Dr. Silver, MD.
Research by Dr. Lindmeier, DHSc, cancer educator and co-author of The New Reality of Cancer.
This article is for general education only and is not individual medical advice. Always consult your own doctor before making any changes to your care.
© 2026 Lovely LYF LLC. All rights reserved. This article draws on the research in The New Reality of Cancer and may not be copied, republished or distributed without written permission.
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References
- Guardant Health. FDA approves new Guardant360 Liquid CDx, the largest FDA-approved liquid biopsy panel. Press release, May 20, 2026.
- Nakamura Y, Taniguchi H, Ikeda M, et al. Clinical utility of circulating tumor DNA sequencing in advanced gastrointestinal cancer: SCRUM-Japan GI-SCREEN and GOZILA studies. Nature Medicine. 2020;26(12):1859–1864.
- Guardant Health, Inc. Quarterly report (Form 10-Q) for the quarter ended September 30, 2026.
- Chung DC, Gray DM, Singh H, et al. A cell-free DNA blood-based test for colorectal cancer screening. New England Journal of Medicine. 2024;390(11):973–983.
This article is for education only. It is not medical advice and does not diagnose or treat any condition. Cancer Expert MD has no financial relationship with any laboratory, drug maker, supplement company, clinic or hospital.
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