Minimal residual disease (MRD) testing is a highly sensitive method used to detect very small numbers of cancer cells that remain in the body after treatment, often at levels far below what imaging or standard blood tests can pick up. It is already standard practice in blood cancers such as leukemia and myeloma, and is rapidly expanding into solid tumours like colorectal, lung, and breast cancer through blood-based tests that track circulating tumor DNA (ctDNA). MRD results are increasingly used to guide whether a patient needs more treatment, less treatment, or closer surveillance. An oncologist can advise whether MRD testing is appropriate for your specific cancer type and stage.
Want to know if MRD testing applies to your treatment plan?
Consult Dr. Namratha Sai Reddy to discuss whether minimal residual disease testing is relevant to your diagnosis, treatment monitoring, or surveillance plan.
Key Takeaways
- MRD testing detects cancer cells left behind after treatment, at a sensitivity imaging cannot match.
- It is an established standard of care in leukemias, lymphomas, and multiple myeloma.
- In colorectal cancer, ctDNA-based MRD testing is now guiding real treatment decisions — the DYNAMIC trial reduced adjuvant chemotherapy use from 27.9% to 15.3% in stage II colon cancer without compromising outcomes.
- In multiple myeloma, MRD-negative patients have shown roughly a 20% lower risk of death compared with MRD-positive patients across pooled trial data.
- MRD is not yet part of routine breast cancer guidelines and remains investigational in most solid tumours outside colorectal and lung cancer.
- A positive MRD result does not always mean visible relapse is imminent, but it significantly raises the risk and often prompts closer monitoring or treatment changes.
When should you discuss MRD testing with your doctor?
If you have completed treatment for a blood cancer, colorectal cancer, or certain other cancers and want to understand your risk of relapse more precisely, or if your oncologist has already recommended surveillance testing, ask specifically whether MRD/ctDNA testing is appropriate for your case.
What Exactly Is Minimal Residual Disease?
Minimal residual disease, sometimes called measurable residual disease refers to the very small numbers of cancer cells that remain in the body after a patient has completed curative-intent treatment, even when scans and standard blood work show no visible signs of disease.
Unlike a CT or PET scan, which can only detect tumours once they reach a certain size, MRD testing works at a molecular level. In blood cancers, this typically means examining bone marrow with flow cytometry or DNA sequencing. In solid tumours, it usually means analysing a blood sample for circulating tumor DNA (ctDNA) — fragments of tumor-derived DNA shed into the bloodstream that clear within hours of a macroscopically complete surgery, meaning any ctDNA detected afterward reflects genuine residual cancer rather than surgical leftover.
Why Is MRD Testing Considered So Important Right Now?
For decades, oncologists have had to make treatment decisions — whether to give more chemotherapy “just in case,” or whether a patient is truly cancer-free — based largely on imaging, blood counts, and statistical risk based on tumor stage. MRD testing offers something different: a direct, molecular readout of whether cancer is actually still present.
This matters because pathological staging alone has real limits. In colorectal cancer, for example, despite complete surgical resection, more than 30% of patients with resectable disease still relapse, and standard staging alone cannot reliably identify which of them.
Can MRD Testing Change Whether a Patient Gets Chemotherapy?
Yes, and this is one of the most significant shifts MRD testing has brought to cancer care.
What the Evidence Says
The DYNAMIC trial, a randomized study in stage II colon cancer, used ctDNA-guided decision-making to determine which patients needed adjuvant chemotherapy after surgery. Patients who were ctDNA-negative were spared chemotherapy, while ctDNA-positive patients received it. The result was a46% lower rate of chemotherapy use in the ctDNA-guided group, with no difference in two-year recurrence-free survival compared with standard treatment.
Japan’s large-scale GALAXY study, part of the CIRCULATE-Japan programme, found something similarly striking: ctDNA positivity after surgery was associated with a nearly 12-fold higher risk of disease recurrence, and patients who achieved sustained ctDNA clearance after chemotherapy had dramatically better two-year disease-free survival than those with persistent positivity (89% versus 3%).
Some experts have urged caution, however — a published debate over the DYNAMIC trial raised concerns about its non-inferiority margin and a notable increase in a chemotherapy drug associated with long-term nerve damage in the ctDNA-guided arm, underscoring that this approach is still being refined.
Is MRD Testing Standard of Care for Blood Cancers?
Yes. MRD testing has the longest track record and strongest evidence base in hematologic malignancies.
The National Comprehensive Cancer Network (NCCN) includes MRD testing in its clinical practice guidelines for acute myeloid leukemia, acute lymphoblastic leukemia (including pediatric ALL), chronic myeloid leukemia, and multiple myeloma. In these cancers, MRD is a major, validated predictor of relapse and directly informs treatment intensity.
What the Evidence Says
In multiple myeloma, a large meta-analysis submitted to the FDA found that conversion to MRD-negative complete response was strongly associated with both progression-free and overall survival, with odds ratios above 4 for both outcomes. This evidence was strong enough that in April 2024, the FDA’s Oncologic Drugs Advisory Committee voted to support MRD-negative complete response as an early endpoint that can be used to support accelerated drug approval in myeloma — a significant milestone, since it means new therapies could reach patients faster based on MRD results rather than waiting years for survival data to mature.
Is MRD Testing Used in Lung Cancer?
Yes, increasingly so, particularly after surgery for early-stage non-small cell lung cancer (NSCLC).
Molecular residual disease analysis is being used to evaluate whether patients on targeted therapies such as osimertinib for resected EGFR-mutated stage IB-IIIA NSCLC are truly disease-free at the molecular level, and consensus frameworks are now being developed by thoracic oncology groups to standardize how ctDNA-based MRD testing should be interpreted and timed in lung cancer specifically, given how much variability currently exists between different assay platforms.
Is MRD Testing Used in Breast Cancer?
Not yet as a standard part of care. MRD testing is not currently included in breast cancer treatment guidelines, and researchers are still studying exactly how and when it might be useful. Patients interested in MRD testing for breast cancer should talk to their oncologist about what, if anything, is appropriate for their specific situation, since much of this remains investigational.
What Other Cancers Are Being Studied for MRD Testing?
MRD/ctDNA research is expanding rapidly beyond its established uses:
- Colorectal liver metastases, where serial ctDNA testing is being studied to predict prognosis and chemotherapy benefit after resection
- Prostate cancer, where trials are evaluating MRD to predict treatment efficacy in metastatic hormone-sensitive disease
- Endometrial and cervical cancer, where prospective studies are testing whether ctDNA can detect recurrence earlier than standard imaging
- Solid tumours broadly, where a 2026 review describes ctDNA as an emerging dynamic biomarker for real-time cancer monitoring across multiple tumour types
How Is MRD Testing Different from Standard Cancer Follow-Up?
- Standard imaging (CT, PET, MRI) can only detect tumours once they reach a visible size; MRD testing works at a molecular level, detecting disease months before it would show up on a scan.
- MRD testing is a type of personalized medicine — results are specific to the individual patient’s tumor and used directly to tailor their treatment plan, rather than applying population-level statistics.
- In cancers where it is validated, MRD status is a stronger predictor of outcome than most conventional risk factors — in one multiple myeloma study, MRD-negative status was a more powerful predictor of survival than high-risk genetic markers.
- It is not yet available or validated for every cancer type — its role varies considerably depending on the specific diagnosis.
How Is MRD Testing Done?
Depending on the cancer type, MRD testing may involve:
- Bone marrow analysis using multiparameter flow cytometry or next-generation sequencing (mainly for blood cancers)
- Blood-based ctDNA testing, either using a “tumor-informed” assay built from the patient’s own tumor tissue, or a “tumor-agnostic” methylation-based assay
- Serial testing over time, since a single result matters less than the trend — persistent positivity or a rising signal carries different implications than a single low-level detection
What Can This Testing Tell Your Doctor?
A tissue-free MRD assay validated in the GALAXY colorectal cancer study demonstrated high specificity and a median lead time of 4.6 months between a positive ctDNA result and clinically detected relapse — meaning MRD testing can flag a recurrence risk months before it would otherwise be caught, giving time to intervene.
Does a Positive MRD Result Always Mean Treatment Should Change?
Not necessarily, and this is an active area of clinical debate. A positive MRD result substantially raises the statistical risk of relapse, but it does not automatically mean more treatment will improve outcomes for every patient. Some researchers have specifically cautioned that the prognostic value of ctDNA does not automatically prove that additional treatment based on a positive result will improve survival — this is exactly why large randomized trials, rather than observational data alone, are needed before MRD-guided treatment changes become routine in a given cancer type.
Please do not interpret an MRD result on your own or make treatment decisions based on it without your oncologist’s guidance — the clinical meaning of a positive or negative result varies significantly by cancer type, stage, and the specific assay used.
When Should You Talk to Your Oncologist About MRD Testing?
- You have completed treatment for a leukemia, lymphoma, or multiple myeloma and want to understand your depth of response
- You have had surgery for colorectal cancer and want to discuss whether ctDNA testing could inform your adjuvant treatment plan
- You are being treated for early-stage EGFR-mutated lung cancer and want to understand molecular residual disease monitoring options
- You are considering enrolling in a clinical trial that uses MRD status for eligibility
- You have questions about whether MRD testing is relevant to your specific cancer type, since availability and evidence vary considerably
Considering Whether MRD Testing Fits Your Treatment Plan?
Minimal residual disease testing is reshaping how oncologists monitor treatment response and relapse risk — but its role differs meaningfully from one cancer type to another.
Book a consultation with Dr. Namratha Sai Reddy to discuss whether MRD or ctDNA testing is appropriate for your diagnosis and ongoing care.
Frequently Asked Questions
What does MRD-negative mean?
MRD-negative means that no residual cancer cells were detected by a highly sensitive test, though it does not guarantee that all cancer cells are gone, it means levels are below the test’s detection threshold.
Is MRD testing the same as a regular cancer blood test?
No. Standard blood tests and imaging detect cancer at much lower sensitivity. MRD testing can detect residual disease at levels far too small for conventional methods to catch.
Which cancers use MRD testing most often?
It is most established in leukemias, lymphomas, and multiple myeloma, and is rapidly expanding into colorectal cancer and certain lung cancers.
Can MRD testing replace CT or PET scans?
No, it complements rather than replaces imaging. MRD testing detects molecular-level disease that imaging cannot see, but imaging still plays an important role in overall monitoring.
Does a positive MRD test mean my cancer has come back?
Not necessarily. It means residual cancer cells were detected, which significantly raises relapse risk, but a positive result does not automatically mean visible relapse is imminent or that more treatment is proven to help in every situation.
Can MRD testing help me avoid unnecessary chemotherapy?
In some cancers, yes. In stage II colon cancer, the DYNAMIC trial showed ctDNA-guided care reduced chemotherapy use by nearly half without harming outcomes. This approach is still being refined and isn’t appropriate for every cancer type.
Is MRD testing available for breast cancer?
Not yet as standard care. It is not currently part of breast cancer treatment guidelines and remains under active research.
How is MRD tested in blood cancers versus solid tumours?
Blood cancers typically use bone marrow analysis via flow cytometry or sequencing, while solid tumours generally use blood-based circulating tumor DNA (ctDNA) testing.
How early can MRD testing detect a recurrence?
In one validated colorectal cancer assay, the median lead time between a positive MRD result and clinical relapse was 4.6 months.
Does MRD-negative status guarantee a cure?
No. MRD-negative status is associated with meaningfully better outcomes, but it reflects undetectable disease at the sensitivity of the specific test used, not a guarantee that no cancer cells remain anywhere in the body.
Medical References
- OncoLink — Testing for Measurable/Minimal Residual Disease (MRD)
- ARUP Consult — Minimal Residual Disease Testing
- Kasi, P. et al. “ctDNA-Guided Adjuvant Therapy in Resected Colorectal Cancer.” Biomedicines (2026)
- Tie, J. et al. “Molecular residual disease and efficacy of adjuvant chemotherapy in colorectal cancer.” Nature Medicine (2022)
- The evolving role of ctDNA in colorectal cancer — PMC (2026)
- Additional considerations before using a ctDNA-guided approach in colorectal cancer — PMC
- Minimal Residual Disease as an Early Endpoint for Accelerated Drug Approval in Myeloma — Blood Cancer Discovery, AACR
- MRD Negativity: A “Robust” Predictor of Survival Outcomes in MM — AJMC
- Minimal residual disease status is the prognostic determinant following high-dose treatment for multiple myeloma — PMC
- Consensus Statement on ctDNA MRD Testing in Early Stage NSCLC — ScienceDirect
- Susan G. Komen — MRD Testing in Breast Cancer
- Validation of a methylation-based, tissue-free MRD assay in colorectal cancer — PMC
- Minimal residual disease in solid tumors: Clinical applications and future directions — Cancer, Wiley