What Minimal Residual Disease (MRD) Can Tell You About CLL
- Minimal residual disease (MRD) is an important concept in the treatment of blood cancers.
- MRD shows whether tiny amounts of CLL (chronic lymphocytic leukemia) remain after treatment, even when you feel well and routine tests look normal. Patients who reach “MRD‑negative” — meaning no leukemia cells can be detected at the current testing threshold — tend to have the longest-lasting remissions.
- Different MRD tests have varying levels of sensitivity, which can affect how results are interpreted. Some tests can detect one cancer cell out of 10,000, while newer methods like ClonoSEQ can find one out of a million.
- Being MRD‑negative doesn’t mean cured, but it’s a strong sign of a good long‑term outlook. MRD results are increasingly used to help decide how long treatment should continue and when it may be safe to stop.
MRD, also known as measurable residual disease, refers to the small number of leukemia cells that can remain in the blood or bone marrow even after a patient has responded well to treatment — cells too few to cause symptoms or show up on a routine scan, but potentially still detectable with sensitive lab testing.
Read MoreIf you are MRD-positive, your physician has various strategies to help you achieve an MRD-negative status if needed.
Expert Resources for CLL Patients
- Changing the Way CLL is Treated: What are BTK Inhibitors?
- Determining Your CLL Treatment: Why Stage Is Only Part of the Picture
- Determining When CLL Treatment is Needed
- BTK Inhibitors: Finding The Right Fit For Chronic Lymphocytic Leukemia (CLL) Patients
- After the Initial CLL Diagnosis: The First Conversation
Why the Technology Used to Test for MRD Matters
Not all MRD tests are equally sensitive, and Dr. Bhushan emphasized that this matters for interpreting results.
“It depends on your technique,” he says. “If you can pick up one in a hundred cancer cells, there are patients who have one in a million cancer cells that you’re missing out on.”
Three types of tests are used clinically to detect MRD in CLL:
- Flow cytometry, a widely used, cost-effective lab method.
- ClonoSEQ, a next-generation sequencing (NGS)-based test.
- PCR-based methods (a related molecular technique).
The standard clinical threshold for “undetectable MRD” is one leukemia cell per 10,000 normal cells (a sensitivity of 1 in 10,000, or 10⁻⁴) — the level Dr. Bhushan referenced. But some technologies can go deeper. ClonoSEQ, in particular, can detect disease at roughly one cell per million (10⁻⁶), a full two orders of magnitude more sensitive than the standard threshold.
MRD-Negative Doesn’t Mean Cured
Reaching undetectable status is a strong prognostic sign, but it isn’t a guarantee the disease is gone for good.
“It doesn’t mean that if you’re MRD-negative, you’re cured forever,” Dr. Bhushan notes. “These patients who are zero out of 10,000 may have one out of a million cells that tends to come back.”
He also pointed out that as testing technology becomes more sensitive, the clinical bar for what counts as “MRD-negative” is likely to shift over time.
MRD status is no longer just a research tool used to measure how well a drug worked after the fact. It’s increasingly being used in real time to decide when a patient can safely stop treatment.
“Nowadays, actually, many of the trials now base the duration of treatment on MRD negativity,” he says.
Questions for Your Doctor
- Should I be tested for MRD, and which test is most appropriate for me?
- What does my MRD status mean for my long‑term outlook and treatment plan?
- If my MRD test shows I’m still MRD‑positive, what options do we have to try to reach MRD‑negative?
- Could my MRD results help determine how long I need to stay on treatment or when it might be safe to stop?
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