Minimal residual disease (MRD) refers to the small number of cancer cells that may remain in a patient’s body after undergoing treatment for their cancer, even when the patient shows no signs of disease, according to theNational Cancer Institute.
Being able to understand the concept of MRD is important for patients with cancer as they continue to undergo treatment, as testing for MRD is something that is expected to be much more commonly used, according to Dr. Christopher R. Flowers, who added that there is hope that MRD testing may serve as an intervention to help address the cancer before it even becomes more widespread.
In an interview with CURE®, Flowers, who works in the Department of Lymphoma — Myeloma, Division of Cancer Medicine, at The University of Texas MD Anderson Cancer Center, in Houston, delved into the topic of MRD and MRD testing in cancer care, explaining why this is an important concept for patients to understand and what this means in terms of risk for recurrence and how to interpret this information.
CURE: Could you explain what MRD is and why it is important for patients to understand?
Flowers: That's a challenging question to start off with [on the] topic of MRD. The term MRD is interpreted in different ways and the term stands for different things in different settings; however, the most common use of MRD is for minimal residual disease, and this can be detected by a number of different methods, using different tools. Essentially, what it means is detecting disease at a level that can't be detected by typical methods like a CT scan or other imaging tests like an MRI, detecting it at a level that is below clinical detection using those typical approaches.
For patients who are told they have MRD, what does this mean in terms of their risk for cancer recurrence, and how should they interpret this information?
This can mean different things for different cancers, and so there's not one single interpretation for that. Oftentimes, what it means is that for a patient who has undergone a typical evaluation after completion of their treatment — like with CT scans or with typical blood tests — to know whether there's any evidence of disease, and all of those tests come back negative, showing that there's no detectable disease, by traditional means, and then to have some form of a blood based MRD test. Now, for different diseases, that can be a different kind of test, so that could be things like flow cytometry that is able to detect, to a very small level, circulating cells from cancer. It could be a test like a genomic or genetic test, where it can detect evidence of the genes that are associated with that cancer even though you can't detect levels of that cancer itself that are circulating in the bloodstream. That result can mean that there is some likelihood of the cancer coming back at a later date related to that test being positive.
There is the possibility, in some settings, of that being a false positive test, so that's something that's also important to keep in mind; the test could come back positive, but there really is not detectable cancer in that setting. That's much less common for these kinds of tests, but that still can occur. For different cancers, the detection of MRD means different things. For some cancers that might be more rapidly growing, that may be a sign that the cancer is coming back in a relatively short period of time. For other kinds of cancers that may be slower growing, it may mean that there's a need for continuing monitoring over time.
In your experience, how does identifying MRD influence decisions about follow up care, monitoring or additional treatments?
Those are all things that we're still working out for different cancers. For some of the cancers that I deal most commonly with, like the lymphomas, these are tests that are now just emerging, and tests that we will be bringing into clinical practice guidelines in the future. For other cancers, the guidelines are becoming more established, and MRD testing will be part of the routine follow-up care in the relatively near future. There will be monitoring strategies that are connected to that follow up as well.
To your knowledge, are there any specific types of cancers or stages of disease where MRD detection has been proven to be especially beneficial for guiding patient care?
That's still an emerging science, but the places where it is much more commonly used are diseases like acute myelogenous leukemia, where it's used for the blood cancers; it's now emerging for other cancers like colorectal cancers and more common cancers like breast cancer in the relatively near future.
How do you see the role of MRD evolving in cancer care as time goes on?
[MRD testing is something] that's going to be much more commonly used, potentially in the distant future, as an early detection method. This [may be used] for patients who have a risk of cancer in the near future as an approach for identifying relapse of cancer earlier. [We hope to eventually], hopefully have interventions that help to address that condition before the cancer becomes more widespread.
Transcript was edited for clarity and conciseness.
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