Minimal residual disease (MRD) refers to the small number of cancer cells that are left in your body after cancer treatment.

MRD is a measure used for multiple myeloma, lymphoma, leukemia, and other blood cancers. An MRD test looks for any cancer cells that were not killed by chemotherapy or other cancer treatments.

An MRD test can help determine if you’re in full remission, if you’re at risk of relapse, and if further treatment is needed.

Read on to learn more about MRD, how tests can detect its presence, and what treatment may be needed to address MRD.

MRD refers to the small number of cancer cells that remain in your body after cancer treatment is complete.

Often, the number of remaining cells is too small to cause any signs or symptoms. In fact, the number is too small to even be detected through traditional methods, such as complete blood counts or tracking serum proteins in your blood.

An MRD test can find remaining cancer cells even in very small numbers. MRD tests use very sensitive methods that can find even a single cancer cell in 1 million healthy cells. These include testing methods such as:

  • multiparametric flow cytometry
  • polymerase chain reaction (PCR)
  • next generation sequencing (NGS)

These tests are often used after initial treatments for multiple myeloma and other blood cancers to show:

  • how well your body responded to treatment
  • if you’re in full remission, especially to check if remission is stable
  • if you’re in recurrence

MRD testing is done using three primary methods. These methods require samples of bone marrow cells or blood cells. You’ll need to have a bone aspiration or blood draw before you can have an MRD test.

MRD methods include:

  • Flow cytometry. Flow cytometry uses a sample of bone marrow cells. The method uses antibodies to check for the absence or presence of important protein markers on cell surfaces. It can find cancer cells even if there is only one in a group of 100,000 healthy cells.
  • PCR. PCR looks for atypical genetic characteristics in specific segments of DNA. The test expands the DNA to make it easier to detect and count atypical characterstics. It can be done with bone marrow or blood cells. PCR tests can find cancer cells if there is only one in groups of 100,000 to 1 million healthy cells.
  • NGS. NGS testing can quickly examine stretches of DNA or RNA to look for atypical genetic characteristics. It uses bone marrow samples and can find one cancer cell in a group of 1 million healthy cells.

A bone marrow aspiration is an outpatient procedure. Here’s how the test is generally done:

  1. You’ll be given a local anesthetic to numb the spot. If you’re nervous, the doctor might give you a sedative to help you relax. You might receive both the sedative and a pain medication through an intravenous (IV) line during the aspiration.
  2. You’ll lay on your side during the procedure. Generally, bone marrow is drawn from the area at the top of your hip bone. Your chest bone might also be used.
  3. Once the area is numb, the doctor will insert a hollow needle into the bone and withdraw fluid from your bone marrow. You might feel a dull aching sensation while the needle is in your bone.

It’s common to be sore for about a week following your bone marrow aspiration. You can usually manage this at home with over-the-counter pain relievers. Follow any instructions you receive to keep your insertion site clean.

Flow cytometry results take about a day. PCR and NGS results take about a week.

A negative MRD result means that no cancers were found. This means there is no more cancer left in your body and the treatment has been effective.

Studies have demonstrated that negative MRD tests are associated with longer remissions and better overall outcomes for multiple melanomas and other types of blood cancer.

A positive MRD test means that cancer cells were found. This does not necessarily mean you’re no longer in remission, but it does mean there is a risk of the cancer returning. This result also might indicate that you and the doctor may need to discuss new treatment options.

An MRD test can help you and your team determine the next steps.

A negative MRD test indicates that you do not need further treatment right now.

A positive MRD test indicates that it might be time for the next steps. Options will depend on:

  • treatments you’ve already had
  • the specific type of blood cancer you have
  • your overall health
  • how many cancer cells were found

Possible treatment options after a positive MRD test might include:

MRD tests are highly specialized. They’re not offered at all labs. They might require you to use a lab that’s not in your insurance plan’s network.

Additionally, MRD tests often require prior authorization. If the doctor recommends an MRD test, talk with your insurance provider to see what’s covered. Some Medicare plans also cover MRD tests.

Keep in mind that even if your insurance provider covers the cost, you might need to cover copayments, insurance payments, or your deductible.

The costs of MRD testing without insurance will depend on your location, the lab you use, the exact test, and other factors, but average costs are over $3,500.

A positive MRD result means that there are cancer cells in your blood. This does not always mean you’ll relapse, but it does indicate that you might need further treatment. A doctor will let you know what a positive MRD result means in your specific case.

It’s important to know that a negative MRD result does not mean it’s impossible for you to have a relapse. It means that there are currently no cancer cells in your body. But you’ll need to be monitored for relapses and be alert for any symptoms that might signal the cancer has returned.

Your outlook depends on:

  • the type of blood cancer you have
  • what treatments you’ve already had
  • what treatments your doctor orders going forward
  • how many cancer cells were found in your MRD testing

Talk with a doctor to make sure you understand exactly what a positive MRD result means for the blood cancer you have. Negative MRD tests are generally associated with a better outlook in all blood cancers.