What Is Measurable Residual Disease (MRD)?
If you were diagnosed with acute lymphocytic leukemia (ALL) or another type of blood cancer, there’s a chance that you’ve heard the term measurable residual disease (MRD) after completing your treatment course. But what is it, and what does it mean for you?
MRD, which previously stood for minimal residual disease, describes the small number of cancer cells that remain in your body after treatment. Though it can be confusing at times, MRD testing can sometimes offer valuable information, including how effective your treatment was and potential next steps.
Patient Power spoke to Eunice Wang, MD, chief of the leukemia service at Roswell Park Comprehensive Cancer Center in Buffalo, New York, about what patients can take away from MRD results and what the future may hold as MRD testing is being studied in a variety of blood cancers.
What Can MRD Tests Find?
The few remaining cancer cells in the body after treatment are not apparent using the same tests that doctors initially used when they diagnosed you. Doctors use MRD tests to find remaining cancer cells in the blood or bone marrow that were not eradicated.
The tests allow doctors to inspect your cells at a deep level to measure your disease. The most commonly used tests are flow cytometry, polymerase chain reaction, and next-generation sequencing. These tests are sometimes done using bone marrow cells collected from a bone marrow aspiration – a procedure that removes a small amount of bone marrow. They may also be done on peripheral blood cells taken through a simple blood draw from a patient’s vein. Uncertainties remain about which test is best and what sample type to use.
Some MRD tests can measure how many cancer cells remain in your body for every 10,000 cells. Others can even detect how many cancer cells remain out of 1 million.
A negative MRD result means that there are no detectable cancer cells left in your body and indicates that your therapy was effective. When signs of your cancer in the blood and bone marrow disappear, your doctor may refer to it as a complete response or complete remission.
Doctors sometimes use the phrase MRD-positive to describe test results showing that cancer cells are still present. Depending on the results, your doctor may want to discuss further treatment options.
MRD Testing for Different Cancers
MRD is part of routine testing for acute lymphocytic leukemia (ALL) patients following a course of treatment. It’s especially useful because time is often of the essence, and treatment decisions need to be made soon after a diagnosis. It’s also useful because MRD status can guide treatment with a Food and Drug Administration-approved therapy.
Researchers and doctors have less information about the significance of MRD testing for other blood cancers, Dr. Wang explained. Several clinical trials are looking at how MRD might play a future role in other blood cancers. For instance, recent clinical studies examining whether patients with chronic myeloid leukemia (CML) can safely stop therapy, using MRD tests to help make that determination and for continued monitoring. MRD testing for chronic lymphocytic leukemia (CLL) may also show which patients may benefit from different treatment intensities and maintenance strategies. MRD is also increasingly being studied in patients with multiple myeloma and lymphoma to predict response to treatment and prognosis.
MRD Can Affect Treatment Decisions
MRD testing is among the ways doctors can personalize medicine and your treatment.
Results from an MRD test for patients with ALL could indicate they need more chemotherapy, another treatment, or a bone marrow transplant. The immunotherapy drug blinatumomab (Blincyto) is approved to treat certain patients with ALL in remission who have MRD-positive disease.
Assessing MRD status often leads to conversations with your doctor about balancing potentially harmful side effects with the benefits of receiving more treatment. There may be so few remaining cancer cells that your own body may be able to take care of it in certain cases, Dr. Wang said.
“It’s like you’re in a fight. You’re fighting cancer; you’ve gotten this almost defeated; and you’ve got the cancer on its knees. You just want to do the knockout punch," Dr. Wang said. “This is the best time to cure the disease."
With newer targeted therapies, she added, doctors want to know MRD status to administer further treatment. This is especially important because MRD testing can detect if a patient relapses earlier than other tests.
Treatments for ALL and other blood cancers have become more effective over the past years. MRD testing has helped doctors and patients decide which treatment options may work best, Dr. Wang said. This might even mean choosing between one treatment that works only slightly better than another.
“That should be construed by patients as very positive information. We have so many new drugs available for your disease, and we have so many drugs that are effective that we’re at the point where we’re trying to detect the minimum amount of disease in patients,” Dr. Wang said. “We’re really fine-tuning things.”
How Much Do MRD Tests Cost?
MRD testing is a specialized procedure and not all centers can perform them. If you are a patient with ALL, the cost of MRD testing is typically covered by insurance because it is well established and accepted by medical experts as the standard of care.
However, for other types of cancers, private insurance coverage for MRD testing may be tricky. In those instances, Dr. Wang said clinical trials may be able to offer patients a way to receive MRD testing at no cost. Additionally, participating in these clinical trials could help researchers further their understanding for future uses.