ctDNA vs MRD vs MCED Testing: Differences, Uses, Accuracy and Evidence (2026)

Updated: October 16, 2026

Quick answer: What is the difference?

• ctDNA testing: Looks for tumor-derived DNA fragments and, depending on the assay, genetic changes associated with a cancer.
• MRD testing: Looks for evidence of a very small amount of residual cancer, often after treatment. It can use ctDNA or other highly sensitive laboratory methods.
• MCED testing: Screens for signals associated with multiple cancers in people who do not have a known cancer diagnosis.

ctDNA vs MRD vs MCED testing: These three terms are closely related in modern cancer diagnostics, but they answer different clinical questions. Circulating tumor DNA (ctDNA) is a biological signal that can be measured in blood. Minimal or measurable residual disease (MRD) describes small amounts of cancer that remain in the body during or after treatment. Multi-cancer early detection (MCED) testing aims to screen people without a known cancer diagnosis for signals associated with multiple cancers.

Although all three approaches may involve a blood test, they are not interchangeable. Their intended populations, laboratory methods, clinical applications and limitations differ.

This guide explains how the tests work, when they may be useful, what positive or negative results mean, and what the latest evidence says about their ability to improve cancer outcomes.

The simplest way to remember the distinction: ctDNA is a biological signal, MRD is a residual-disease question, and MCED is a multi-cancer screening approach.

Important: A negative result from any of these tests does not reliably exclude every cancer. An abnormal result does not automatically establish a cancer diagnosis or prove that changing treatment will improve survival.

Table of Contents

1. ctDNA vs MRD vs MCED: comparison table
2. What is ctDNA testing?
3. What is MRD testing?
4. What is MCED testing?
5. How do these tests overlap?
6. Accuracy, sensitivity and false results
7. Latest evidence and research in 2026
8. Which test is appropriate for each situation?
9. Questions to ask before testing
10. Frequently asked questions
11. References and further reading

1. ctDNA vs MRD vs MCED: Comparison Table

The most important difference is the clinical question being asked. The same general laboratory technology may contribute to more than one type of test, but that does not make their purposes identical.

↔ Swipe the table sideways to see all columns on mobile.

Feature	ctDNA testing	MRD testing	MCED testing
Full name	Circulating tumor DNA	Minimal or measurable residual disease	Multi-cancer early detection
Main question	Can tumor-derived DNA or a relevant tumor alteration be detected?	Is there evidence of residual cancer?	Is there a signal suggesting an otherwise undiagnosed cancer?
Typical population	People with known or suspected cancer, depending on the indication	People with cancer being assessed during or after treatment	People without a known cancer diagnosis
Primary purpose	Genomic profiling and selected forms of monitoring	Assess residual disease and, in appropriate settings, recurrence risk	Screen for signals associated with multiple cancers
Common sample	Usually blood plasma	Blood, bone marrow or another sample, depending on the cancer and method	Usually blood; other body fluids may be used by some tests
Possible methods	PCR, digital PCR or DNA sequencing	Flow cytometry, PCR, sequencing or other validated molecular methods	DNA methylation, DNA sequence or fragmentation patterns, and other cancer-associated signals
Positive result means	A target signal was detected; interpretation depends on the assay	Evidence of residual disease was detected according to the test's definition	A signal associated with possible cancer was detected
Negative result means	The tested signal was not detected at the assay's sensitivity	Residual disease was not detected by that method	No target signal was detected by the screening test
Key limitation	Some cancers shed little DNA, and not all alterations are detectable	Clinical significance and treatment implications differ across cancer types	False positives, missed cancers and the effect on cancer deaths remain important concerns

The table describes broad categories, not the performance of a particular commercial assay. Accuracy and clinical usefulness depend on the test, cancer type, disease stage and intended use.

2. What Is ctDNA Testing?

Circulating tumor DNA (ctDNA) consists of small DNA fragments released into the bloodstream by tumor cells. A blood test can analyze these fragments to look for genetic alterations or other measurable characteristics associated with a tumor.

ctDNA is part of the broader field of liquid biopsy. Instead of obtaining tumor tissue directly, a liquid biopsy analyzes a biological sample, most commonly blood, for cancer-associated material.

For a basic definition, see the National Cancer Institute's explanation of ctDNA.

How does ctDNA testing work?

1. Blood collection: A blood sample is collected using the appropriate laboratory collection system.
2. Sample processing: The laboratory separates plasma or prepares the specimen according to the test's requirements.
3. Molecular analysis: The laboratory uses a method such as DNA sequencing or PCR to identify the specific signals the assay is designed to detect.
4. Clinical interpretation: Results are interpreted alongside the cancer diagnosis, tissue findings, imaging, treatment history and other relevant information.

What can ctDNA testing be used for?

Depending on the cancer type, assay and intended use, ctDNA testing may help clinicians:

• Identify treatment-relevant genetic alterations: Certain alterations may help determine whether a targeted treatment is appropriate.
• Investigate resistance: In selected settings, testing can identify or monitor genetic alterations associated with resistance to a treatment.
• Monitor molecular changes: Serial measurements may show changes in detectable tumor-derived DNA during therapy.
• Investigate molecular residual disease: Some ctDNA assays are designed to look for molecular evidence of cancer remaining after treatment.

These applications are not equally established. A test validated for identifying treatment-related mutations should not automatically be assumed to be validated for screening healthy people or guiding treatment after surgery.

What are the limitations of ctDNA testing?

A negative ctDNA test does not always mean the cancer is absent. Tumors differ in how much DNA they release into the bloodstream. Some small or biologically distinct tumors may shed very little detectable DNA, and the test may fail to identify an alteration even when it is present in the tumor.

Other limitations include:

• Some cancer-associated changes are below the assay's detection threshold.
• Some genetic variants found in blood may originate from non-tumor blood cells, a phenomenon called clonal hematopoiesis.
• Blood-based findings may disagree with tissue testing, especially when tumor shedding is low or the disease is heterogeneous.
• A molecular change in the blood does not, by itself, prove which treatment will produce the best outcome.

ASCO's 2026 guideline supports ctDNA testing for tumor genetic alterations in selected circumstances, including when tissue testing is difficult, unsafe or unavailable within a clinically useful timeframe. It advises seeking tissue-based confirmation when a negative, inconclusive or discordant result leaves uncertainty and tissue testing is feasible.

Source: ASCO, Circulating Tumor DNA Testing in Solid Tumors and Lymphoma: Clinical Practice Guideline, 2026.

3. What Is MRD Testing?

MRD stands for minimal residual disease or measurable residual disease. It refers to a very small amount of cancer that remains in the body during or after treatment, potentially at levels below what routine examinations or imaging can identify.

The term is especially established in blood cancers, including certain leukemias, lymphomas and plasma-cell disorders. Methods and clinical applications differ by disease.

The National Cancer Institute's MRD definition explains the concept and its use in assessing treatment response and prognosis.

How does MRD testing work?

MRD is a clinical target rather than one specific technology. The test selected depends on the cancer and the biological features that can be measured.

Examples include:

• Flow cytometry: Identifies abnormal cell populations by measuring cellular characteristics. It is used in selected blood cancers.
• PCR-based testing: Looks for specific molecular markers associated with the cancer.
• Next-generation sequencing: Searches for disease-associated genetic sequences with high analytical sensitivity.
• ctDNA-based MRD testing: Looks for tumor-derived DNA in plasma after treatment, particularly in some solid-tumor settings.

These approaches are not interchangeable. Bone marrow MRD testing in a blood cancer, for example, is not the same procedure as a plasma ctDNA assay after colorectal cancer surgery.

Why is MRD testing important?

After treatment intended to cure cancer, standard imaging may show no visible disease. Nevertheless, small numbers of cancer cells could remain below the detection limits of routine methods.

In appropriate cancers and treatment settings, MRD testing may help clinicians:

• Assess depth of treatment response.
• Estimate the risk of relapse or recurrence.
• Classify disease response according to cancer-specific protocols.
• Support treatment decisions where the evidence and guidelines establish a role for the result.

Does MRD positivity mean cancer will definitely return?

No. A positive result can indicate residual disease or a higher risk of recurrence, but the meaning depends on the cancer, the assay, the time of testing and the available clinical evidence. It is not a guarantee that recurrence will occur at a particular time.

Likewise, a negative result means that the test did not detect the target at its sensitivity. It does not prove that every cancer cell has been eliminated.

Example: After colon cancer surgery

A patient has surgery intended to remove a localized colon cancer. A ctDNA-based MRD assay is performed on a blood sample to look for molecular evidence of residual disease. A positive result may indicate a greater risk of recurrence, but whether treatment should change because of that result requires cancer-specific evidence and specialist review.

Does a positive MRD test mean more treatment is always better?

No. Detecting residual disease and demonstrating that a specific intervention improves survival are different things.

For solid tumors and lymphoma, ASCO's 2026 guideline highlights an important evidence gap: although ctDNA-based MRD testing can have clinical validity, evidence that acting on the result improves patient outcomes remains insufficient across the settings reviewed. The guideline does not recommend ctDNA testing generally for recurrence surveillance outside established evidence-based use.

This does not mean that all MRD testing is unhelpful. MRD testing has established roles in selected hematologic malignancies. The appropriate interpretation must be disease-specific, rather than generalized across all cancers.

4. What Is MCED Testing?

MCED means multi-cancer early detection. MCED tests are designed to screen people who have no known cancer diagnosis for signals that may be associated with multiple types of cancer using one sample.

They are being developed partly because established population screening methods cover only a limited number of cancers. A multi-cancer approach might detect signals from cancers for which there is no widely established screening test.

MCED tests are sometimes described as multi-cancer early detection blood tests, multi-cancer detection tests or multi-cancer screening tests.

How does MCED testing work?

The laboratory analyzes blood or another biological sample for signals that may indicate cancer. Different assays use different technologies and should not be treated as a single uniform product category.

Depending on the test, the signals may include:

• DNA methylation patterns, which are chemical modifications associated with changes in gene regulation.
• DNA sequence changes or fragmentation patterns.
• RNA, proteins or other biological markers in selected testing approaches.
• Molecular patterns that may help estimate the tissue or organ where the cancer signal originated.

Some MCED tests analyze DNA-related signals in the blood, but not every MCED assay is simply a ctDNA mutation test. The analytical method, target signals and intended clinical purpose may differ substantially.

What is MCED screening intended to achieve?

The objective is to detect a possible cancer signal before symptoms appear, potentially prompting earlier diagnostic evaluation.

However, MCED is a screening approach, not a cancer diagnosis. When an MCED result is positive, additional investigations are required to establish whether cancer is present, identify its location and determine its type.

Depending on the result, follow-up may involve imaging, laboratory investigations, endoscopy, specialist assessment or a biopsy.

What are the limitations of MCED testing?

MCED tests introduce several important questions:

• Can the test detect early-stage disease? Performance may differ substantially by cancer type and stage.
• Can it locate the source? Some tests estimate a likely tissue of origin, but that prediction still requires clinical confirmation.
• How many cancers are missed? A negative result may occur even when a person has cancer.
• What happens after a positive result? Follow-up testing may be invasive, costly, time-consuming or inconclusive.
• Does screening save lives? This requires evidence of improved health outcomes, not just evidence that the test can detect a signal.

For these reasons, an MCED test should not replace recommended breast, cervical, colorectal, lung or other established screening when indicated.

For further reading, see the American Cancer Society's guide to multi-cancer detection testing.

5. How Do ctDNA, MRD and MCED Overlap?

These terms are related because they can involve overlapping laboratory technologies. The distinction becomes clearer when the biological marker, clinical question and intended population are considered separately.

ctDNA: What is being measured?

ctDNA is tumor-derived DNA circulating in the bloodstream. It describes a biological signal rather than one particular clinical use.

MRD: What disease state is being investigated?

MRD testing looks for residual cancer during or after treatment. ctDNA is one possible way to investigate MRD in selected settings, but MRD can also be assessed by other methods.

MCED: Who is being screened, and for what purpose?

MCED testing seeks signals associated with multiple cancers in people without a known cancer diagnosis. Its goal is early detection rather than the routine measurement of residual disease after treatment.

Can one blood test serve more than one purpose?

A platform may be adapted for different applications, but validation for one purpose does not establish validity for every other purpose.

For example, an assay that identifies a mutation in an advanced tumor may be appropriate for a treatment-selection question. That fact alone does not demonstrate that the assay can reliably detect microscopic residual disease after surgery, or screen an asymptomatic population for multiple cancers.

The clinical question must match the assay's validation, intended use and supporting evidence.

6. Cancer Blood Test Accuracy: Sensitivity, Specificity and False Results

There is no single accuracy percentage for ctDNA, MRD or MCED testing. Accuracy depends on the specific assay, cancer type, disease stage, sample quality and clinical setting.

Understanding four important concepts

Term	Meaning	Why patients should care
Sensitivity	How often a test identifies the target among people who have it.	Lower sensitivity means more cases may be missed.
Specificity	How often a test returns a negative result among people who do not have the target.	Lower specificity generally means more false-positive results.
Positive predictive value	The probability that a positive result corresponds to the target condition in the population tested.	It depends on test performance and how common the condition is in that population.
Clinical utility	Whether using the test to guide care improves outcomes or decisions enough to justify its harms and costs.	A test can detect a signal accurately without proving that acting on it benefits patients.

Why a negative result can be misleading

A cancer may be present even if its signal is below the detection threshold. This can happen when a tumor releases little ctDNA, when an MRD assay cannot detect all residual cancer cells, or when a multi-cancer screening test does not identify a signal from a particular tumor.

A negative result should therefore be interpreted in the context of the test's sensitivity and the person's symptoms, risk factors, imaging results and clinical history.

Why a positive result may not confirm cancer

A positive result can trigger further investigations without ultimately identifying cancer. The signal may be false positive, may not identify the correct cancer type, or may require additional evaluation to establish its significance.

In population screening, the prevalence of cancer also matters. Even a test with high specificity can produce positive results in people who do not have the target cancer, especially when screening a population in which the disease is uncommon.

This is one reason why a screening test needs to be assessed not only for accuracy, but also for the outcomes of the entire process: follow-up investigations, diagnoses, treatment, complications, quality of life and cancer mortality.

7. Latest Evidence in 2026: What Do the Guidelines and Trials Tell Us?

ASCO's 2026 ctDNA guideline: Detection is not the same as clinical benefit

ASCO published its first guideline focused on ctDNA testing in solid tumors and lymphoma in 2026. It distinguishes uses such as identifying tumor genetic alterations from uses such as monitoring recurrence, evaluating prognosis or guiding changes in treatment.

Its practical message is that ctDNA results should be used when the evidence supports a specific clinical action. Testing may help identify relevant genetic alterations when tissue sampling is difficult, unsafe or too slow for a treatment decision. When results are negative, inconclusive or inconsistent with the clinical picture, tissue-based confirmation should be considered where feasible.

For ctDNA-based MRD testing and recurrence monitoring in solid tumors and lymphoma, the guideline emphasizes the gap between demonstrating a relationship with recurrence risk and proving that acting on the result improves outcomes. It does not recommend ctDNA testing generally for recurrence surveillance across these settings.

Patient implication: Before paying for a test to check whether cancer has returned, ask what the result would change in your care and whether that strategy is supported for your specific cancer.

Read the full guideline: Circulating Tumor DNA Testing in Solid Tumors and Lymphoma: ASCO Guideline.

NHS-Galleri trial: Important multi-cancer screening results published in September 2026

The NHS-Galleri randomized trial is one of the major studies evaluating whether a multi-cancer early detection blood test can improve cancer screening outcomes. It enrolled more than 142,000 volunteers aged 50 to 77 in England and evaluated adding the Galleri test to usual care over repeated annual screening rounds.

The first full results were published in the New England Journal of Medicine on September 22, 2026.

The main result matters: After three screening rounds, the trial did not find a lower incidence rate of stage III or IV cancers combined across the 12 prespecified cancer types in the test group compared with usual care alone. The trial's key secondary analysis found a stage IV cancer incidence rate ratio of 0.86 (95% confidence interval 0.74 to 1.00).

Other findings included more early-stage cancers and fewer diagnoses at stage IV in the screening group. These results are of scientific interest, but they do not establish that MCED screening reduces cancer deaths. Further follow-up is needed.

The results illustrate an important distinction: detecting some cancers earlier is not sufficient by itself to establish the overall benefit of a screening program.

Read the study: Effect of Screening with a Multicancer Early-Detection Test on Late-Stage Cancer Diagnosis.

See also the NHS-Galleri trial results summary.

What is the regulatory status of MCED testing?

As of October 2026, the American Cancer Society and National Cancer Institute report that MCED or multi-cancer detection tests have not been approved by the US Food and Drug Administration (FDA). Some tests have been offered as laboratory-developed tests under applicable US laboratory regulations, but market availability should not be confused with FDA approval or proof of screening benefit.

Regulatory requirements differ by country and can change over time. Patients should check the relevant national regulator and ask the testing provider to explain the exact test's regulatory status and evidence.

Regardless of availability, MCED testing should not be considered a replacement for recommended cancer screening or diagnostic evaluation of symptoms.

Sources: American Cancer Society and National Cancer Institute: Cancer Screening Tests.

8. Which Test Is Appropriate for Each Situation?

The most appropriate test depends on the clinical question rather than which technology sounds most advanced.

Situation	Approach to discuss	Important consideration
Advanced cancer and a potentially actionable tumor mutation	ctDNA genomic profiling in an appropriate setting	A negative result may require tissue testing or another assessment.
After surgery for a solid tumor, with concern about microscopic residual disease	ctDNA-based MRD testing when supported by disease-specific evidence	A positive result does not automatically establish the best treatment.
Leukemia, lymphoma or another blood cancer during treatment	Disease-specific MRD testing	The validated method, specimen and interpretation depend on the malignancy.
Person without known cancer considering screening for multiple cancers	MCED testing as a topic for informed discussion or clinical research	Benefits, harms, follow-up pathways and effects on mortality remain important considerations.
New symptoms, abnormal imaging or a suspicious lump	Diagnostic evaluation by a healthcare professional	Do not use a negative blood test to rule out cancer or delay indicated assessment.

Should people without symptoms get an MCED blood test?

There is no universal answer. A person considering an MCED test should understand the limitations, costs, possible false results and follow-up requirements, as well as the lack of established evidence that the approach reduces cancer mortality.

People should continue recommended screening based on their age, personal risk and applicable clinical guidance. Screening decisions should be made with a clinician who can help interpret risk, benefits and possible harms.

9. Questions to Ask Before Paying for a Cancer Blood Test

Commercial cancer testing can be difficult to evaluate because different tests may have different intended uses. Before proceeding, ask the clinician or laboratory the following questions.

1. What is the actual test designed to detect? Is it assessing tumor mutations, molecular residual disease or signals associated with multiple cancers?
2. Has it been validated for my cancer type and clinical situation? Evidence from a different cancer or disease stage may not apply to me.
3. What would a positive result change? Is there an evidence-based treatment or diagnostic pathway that follows?
4. What does a negative result rule out? Ask about sensitivity and the possibility of a false-negative result.
5. What investigations might follow an abnormal result? These could include further imaging, biopsies or specialist assessment.
6. Is the test approved, authorized or offered under a laboratory testing framework in my country? Ask for documentation and the exact intended use.
7. What is the total cost? Include confirmatory testing and follow-up rather than considering only the initial blood test.
8. Is there a clinical trial or established care pathway that is more appropriate? The answer may depend on the cancer, treatment history and available evidence.

Conclusion: ctDNA vs MRD vs MCED Testing

ctDNA, MRD and MCED testing are related fields in cancer diagnostics, but they serve different purposes.

• ctDNA testing measures tumor-derived DNA and can help identify relevant tumor alterations in selected clinical settings.
• MRD testing looks for very small amounts of residual cancer, using ctDNA or other disease-specific methods.
• MCED testing aims to screen people without known cancer for signals associated with several cancers, but its ability to reduce cancer mortality remains unestablished.

The most important question is not simply whether a blood test can detect a cancer-associated signal. It is whether the test is sufficiently reliable for the intended purpose and whether acting on its result improves patient care.

For patients and families, the safest approach is to choose testing according to the cancer type, clinical question, evidence base and a clear plan for interpreting the result. No single blood test should replace indicated tissue diagnosis, imaging, established screening or a clinical assessment of concerning symptoms.

Medical disclaimer: This article is for educational purposes only and is not a substitute for individualized medical advice, diagnosis or treatment. Testing decisions should be discussed with a qualified healthcare professional. Do not delay an investigation or change prescribed cancer treatment on the basis of a blood test alone.

10. Frequently Asked Questions

1. Is ctDNA testing the same as liquid biopsy?

No. Liquid biopsy is a broader term for analyzing biological samples, usually blood, for cancer-associated material. ctDNA is one target that a liquid biopsy can measure. Other approaches may analyze circulating tumor cells, RNA, proteins or additional biomarkers.

2. Is MRD testing the same as ctDNA testing?

No. MRD describes the search for residual cancer, while ctDNA is a type of biological signal. ctDNA can be used in certain MRD assays, but MRD can also be assessed using flow cytometry, PCR, sequencing and other methods, depending on the cancer.

3. Which is better: ctDNA, MRD or MCED?

None is universally better. They are designed for different purposes. ctDNA may support selected genomic treatment decisions, MRD testing assesses residual disease in appropriate settings, and MCED is intended for multi-cancer screening. The relevant comparison is between tests validated for the same clinical purpose.

4. Can ctDNA testing detect cancer before imaging?

ctDNA may reveal molecular evidence in some circumstances before cancer becomes visible on routine imaging. However, performance varies, and the absence of detectable ctDNA does not exclude cancer. The clinical significance of an early molecular signal depends on the disease and whether evidence supports acting on the result.

5. Can MRD testing predict cancer recurrence?

MRD results can provide prognostic information in selected cancers. A positive result may be associated with a higher risk of recurrence, but it does not guarantee that recurrence will happen. Whether treatment changes guided by the result improve survival depends on the cancer and supporting evidence.

6. Can a negative MRD test mean cancer has been cured?

No. A negative result means the test did not detect the residual-disease signal it was designed to measure. Disease below the detection threshold can remain, and the meaning of a negative result depends on the assay and the cancer-specific setting.

7. Can MCED replace mammograms, colonoscopies or other screening tests?

No. MCED testing should not replace recommended screening methods. It also does not replace diagnostic evaluation when symptoms or abnormal findings require investigation.

8. Does MCED testing detect every type of cancer?

No. Detection performance varies among cancer types and stages. Some cancers may not release sufficient detectable signals, and an MCED test can return a negative result even when cancer is present.

9. Does an MCED-positive result mean someone definitely has cancer?

No. A positive screening result indicates that further evaluation may be needed. Additional diagnostic procedures are required to determine whether cancer is present and, if so, to identify its location and type.

10. Are multi-cancer early detection blood tests proven to save lives?

As of October 2026, a reduction in cancer mortality has not been established for MCED screening. The first full NHS-Galleri trial results, published in September 2026, did not show a reduction in the overall rate of stage III and IV cancers combined across the 12 prespecified cancer types. Further follow-up and research are needed.

11. Are ctDNA and MCED tests FDA-approved?

Regulatory status depends on the specific test and its intended use. Some blood-based molecular tests have authorized clinical applications, while MCED tests had not been approved by the US FDA according to authoritative US cancer information available in October 2026. The status of an individual test should be verified with the relevant regulator.

12. What is the most important question before ordering any of these tests?

Ask whether the result will change a clinical decision in a way that is supported by evidence. A test can detect a biological signal without proving that a particular treatment, extra scan or earlier intervention will improve health outcomes.

11. References and Further Reading

1. American Society of Clinical Oncology (ASCO). Circulating Tumor DNA Testing in Solid Tumors and Lymphoma: ASCO Guideline (2026). Read the guideline.
2. National Cancer Institute (NCI). Definition of circulating tumor DNA (ctDNA). Read the definition.
3. National Cancer Institute (NCI). Definition of minimal residual disease. Read the definition.
4. American Cancer Society. Multi-cancer Detection (MCD) Tests. Read the patient guide.
5. National Cancer Institute (NCI). Cancer Screening Tests. Read the overview.
6. Sasieni P, et al. Effect of Screening with a Multicancer Early-Detection Test on Late-Stage Cancer Diagnosis. New England Journal of Medicine. Published September 22, 2026; 395:1374–1386. Read the study.
7. NHS-Galleri Trial. What the trial found: results from the multi-cancer early detection screening study. Read the trial summary.
8. US Food and Drug Administration (FDA). Use of Circulating Tumor Deoxyribonucleic Acid for Early-Stage Solid Tumor Drug Development: Guidance for Industry. Read the guidance.
9. Multi-cancer early detection (MCED) blood tests in 2026: Galleri vs Cancerguard and the Future of Early Cancer Detection.

Editorial note: Evidence and regulatory status are evolving. References should be checked periodically for new clinical guidelines, trial follow-up and changes in the authorized uses of individual assays.