Another Test? The What, How, and Why of Minimal Residual Disease Testing

One of the newer developments in the cancer testing and diagnostic space is the rise of minimal residual disease (MRD) testing. However, there can be confusion surrounding what it is, how it works, and whether it’s a good fit for you or not. With the rapid rise of new diagnostic technologies and lab tests, it can be hard to know where to turn and what’s best for you. Dive in as we demystify the what, how, and why of MRD testing, and shed some light on this exciting new subject!  

What is minimal residual disease (MRD) testing? 

The goal of curative cancer treatment is to eliminate every single cancer cell circulating in the body. It is necessary to ensure that all cancer cells are eliminated because it only takes a single cancer cell to divide for cancer to begin growing and spreading throughout the body. This means that removing or eliminating a tumor does not guarantee that all cancer cells have been eliminated, so we often see treatment given even after surgical removal of a tumor. MRD testing is a new modality that aims to help patients and providers know how much, if any, cancer remains in the body after definitive treatment. In addition, MRD testing has the potential to help oncologists identify a possible cancer recurrence before it would be visible on a CT or PET scan.  

How does MRD testing work? 

There are a few different techniques that scientists can use to determine the presence and load of cancer cells circulating within the body. One thing they have in common is that they all involve looking for pieces of cancer DNA present in the body’s blood and tissues. One method of MRD testing involves taking a sample of a person’s cancer tumor to identify its unique DNA profile. Once the unique genetic code for the cancer is obtained, blood samples taken from the individual can be analyzed to search for any microscopic DNA fragments that match this genetic signature. If any are found, it could be a sign that the cancer cells are still present/returning, and that further workup and treatment may be needed. Because this method is highly personalized to the individual and their cancer, there is a much lower chance of a false positive. However, this also means that this testing style can take longer to process and can be more expensive.  

The other common type of MRD testing relies on circulating genes and proteins in the body, rather than highly specific, personalized cancer DNA detection. Because of the unique ways cancer cells grow/divide and interact with cells in the body, they have certain markers that differentiate them from the normal cells and proteins in the body. The presence of some of these markers can indicate that an abnormal process is taking place in the body, alerting providers to the possibility of cancer, and indicating an opportunity for further evaluation and testing. Because this method isn’t individualized to a person’s tumor, it can be completed more quickly and cheaply. However, there is also a greater risk for false positives, as the tests primarily look at markers of abnormal DNA and cellular growth, and could have other underlying causes. Some examples of these broad MRD tests are the Oncomine cfDNA Assay by Thermo Fisher and Inivata’s InVisionFirst-Lung test. 

Is MRD testing right for me? 

There are currently a couple of common uses for MRD tests in the real-world setting. The first, as mentioned above, is used after definitive lung cancer treatment, such as surgical removal of the tumor followed by adjuvant chemotherapy. After treatment, your care team may want to perform MRD testing to ensure that there are no surviving cancer cells that were missed by treatment that could go on to spread and cause a recurrence. Another use of this sort of testing still being studied is predictive testing for response to therapy. This means that the results of the MRD test may be used to indicate which patients are going to have a better response to treatment than others. In a study published in 2017 by Abbosh et. al, the findings showed that individuals who had a high MRD concentration after treatment with adjuvant chemotherapy were more likely to experience relapse/recurrence within a year compared to those who had lower MRD testing results.  

If you are interested in MRD testing and want to know if it could benefit you, please be sure to discuss it with your oncologist and cancer care team. Some questions you may consider asking include: 

• Is minimal residual disease (MRD) testing something that could provide additional information, treatment, and response for my cancer? 

• Is this something that is covered by my insurance, and is available through an insurance-approved laboratory? 

• How would you use the findings of this test when treating my cancer? 

• Are there any specific tests that would be best for my unique situation?   

How accessible is MRD testing? 

There are several types of commercially available MRD tests, though the exact availability of these tests can vary by location. However, as the use of science behind these tests grows, access and coverage have also increased. Certain types of testing are covered by insurers and the Medicare/Medicaid programs (though again, this can vary from state to state). For a test to be approved by insurance, it generally needs to be approved for the intended use and have strong scientific evidence supporting it. For certain tests/insurers, prior authorization may be required as well. If you are interested in learning if MRD testing is eligible for coverage under your health plan, it is always best to check your insurance coverage and consult with your healthcare provider.