Introduction:
MRD (Minimal Residual Technique) tests how well the treatment for cancer works and the future implications of the treatment protocol. It is primarily implicated in blood cancers such as leukemia, lymphoma, myeloma, etc. Further studies are being conducted on its implication in other cancer treatments.
What Is MRD?
MRD or minimal residual diseases are the remnants of cancer that persist even after cancer treatment. After treatment, they are the remaining parts of primary tumors present in the body, which also remain unidentified by high-resolution imaging techniques. The presence of MRD reveals possible short- or long-term recurrence in cancer patients. It is a vital indicator of treatment response, so it becomes essential to check for the presence of MRD and treat it in the earliest identification stage, which will help prevent the development of untreatable metastatic illness. It also refers to the persistence of malignant cells in patients who receive successful initial treatment. This MRD can potentially result in metastatic relapse at remote sites. MRD testing and monitoring are already widely used in hematological malignancies but still need to be more challenging to apply in solid tumors due to the low blood levels of CTCs, making sampling challenging. MRD is considered an essential tool in myeloid malignancies and helps in prognostication, disease monitoring, identifying early relapse, guiding post-remission treatment, and measuring the efficacy of the treatment.
What Is MRD Testing?
MRD testing is a method for detecting minimal residual diseases. It is done using three main methods mainly. These methods are implemented by drawing samples of bone marrow cells or blood cells. A person needs to have a bone aspiration or blood draw before they can have an MRD test. MRD tests have very sensitive methods that can detect even a single cancer cell in one million healthy cells. These include testing methods such as:
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Multiparametric flow cytometry.
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Polymerase Chain Reaction (PCR).
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Next-Generation Sequencing (NGS).
Why Is MRD Testing Done?
Cancer treatment primarily aims to destroy as many cancerous cells as possible. If these cells persist, they can result in the multiplication and formation of various other cells. MRD tests can help a doctor determine if the remnants of cancer cells are present or not after the treatment. These tests are often implemented after the completion of primary treatments for multiple myeloma and various other blood cancers to examine:
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In what way does the body respond to treatment?
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If the patient is in complete remission, check if remission is stable.
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If the cancer is in the recurrence stage or not.
When Is MRD Testing Recommended?
The doctor recommends the use of MRD testing in a particular situation. For example, the doctor might recommend MRD testing:
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After the completion of a final cycle of planned combination therapy.
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After the transplantation of a stem cell.
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While the treatment is going on, to confirm the depth of remission.
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At the one-year point of maintenance therapy.
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At regular intervals after the completion of treatment.
What Are the Methods of MRD Testing?
MRD testing uses various advanced methods to detect minimal residual disease. The method depends on the type of blood cancer a person has. The methods used widely for testing MRD include with high sensitivity are:
Flow Cytometry: Flow cytometry is a process that is performed by drawing a sample of bone marrow cells. Antibodies check for the absence or presence of important protein markers on cell surfaces. It can identify cancer cells even if there is a single cell in a group of one lacs of healthy cells.
PCR: PCR (Polymerase Chain Reaction) detects atypical genetic characteristics in particular fragments of DNA (deoxyribonucleic acid). This test makes detecting and counting atypical characteristics easier by expanding the DNA. It can be done with the help of bone marrow or blood cells. PCR tests can recognize cancer cells if there is a single cancerous cell in a cluster of 100,000 to 1 million healthy cells.
NGS: NGS (Next-Generation Sequencing) testing can quickly examine fragments of DNA or RNA (ribonucleic acid) to check for atypical genetic characteristics. It is done with the help of bone marrow samples and can detect one cancer cell in a group of 1 million healthy cells.
What Do the Results of MRD Testing Mean?
The results of MRD testing can signify the following:
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A negative MRD result indicates that there were no cancer cells detected. This means no more cancer is left in the body, and the treatment has been effectively completed. Various research has shown that the presence of negative MRD tests has more prolonged remissions and better overall results for multiple melanomas and other forms of blood cancer.
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A positive MRD indicates that cancer cells were detected. This does not necessarily mean that a person is no longer in remission, but it indicates a possible risk of cancer returning. This result may also indicate that the doctor must identify new treatment options.
Is There Any Side Effect of MRD Testing?
There is no severe side effect of MRD testing. A person may feel discomfort by drawing a blood or bone marrow sample for the MRD test in a few instances. A person should consult the doctor immediately and ask whether pain medication is available.
Is MRD testing Done More than Once?
The doctor and patient decide whether more than one MRD test is required. For example, a positive MRD result might indicate that a person should begin additional treatment. A follow-up MRD test might be advised to see if the new treatment is effective. If the doctor recommends repeat testing, the blood or bone marrow should be sent to the same lab that handled the previous MRD tests. Using the same lab will give the patient and doctor's team accurate comparisons about the MRD status.
Conclusion:
MRD or minimal residual disease are the remnants of cancer already treated. It might remain after the initial treatment. MRD testing is done to identify the treatment efficacy and plan further treatment options. PCR, flow cytometry, etc can do this testing.
