What are MSI and MMR?
MSI stands for MicroSatellite Instability, and MMR stands for MisMatch Repair. They are both biomarkers that are commonly tested to identify if Immunotherapy is likely to work or not in cancer. When cells in the body divide, any errors in the genetic makeup of the cells are repaired. These mistakes are identified and fixed through a mismatch repair system with the help of mismatch repair proteins. If the cells cannot repair these mistakes due to the mismatch repair proteins not working correctly, then the errors in the DNA start to accumulate in the divided cells and may result in cancers. This mistake can happen in a random cell (somatic) or can also be hereditary. When this happens, one can end up with High MicroSatellite Instability (MSI-H) due to deficient MisMatch Repair proteins (dMMR). If cancer is identified to have MSI-H / dMMR, then Immunotherapy is likely to be effective. It can also identify hereditary cancers that may run in families.
How to test for MSI and MMR?
MSI and MMR are tested in different ways. Both the methods are easily available in all major laboratories that do cancer testing.
MSI is a Polymerase Chain Reaction (PCR) test that compares tumour tissue to normal tissue to measure microsatellite instability.
MMR is an Immunohistochemistry (IHC) test that is tested on the tumour tissues of cancer or when the cancer tissue is surgically removed for mismatch-related proteins such as MLH1, MSH2, MSH6, PMS2. Usually, these proteins are present, and if any of these proteins are not expressed in the IHC test, then it is deficient MMR.
Who should be tested for MSI / MMR?
MSI-H or dMMR can be seen in a variety of cancers and is commonly tested in most of them. Colon cancers, Gastrointestinal cancers, and Endometrial cancers have a relatively high proportion of MSI-H / dMMR biomarkers.
What is the benefit of testing for MSI / MMR?
If cancer is identified to have MSI-H / dMMR, then Immunotherapy is likely to be an effective way of treating patients.
The presence of MSI-H / dMMR can also indicate if there is a possibility of hereditary cancers that may run in families, and further genetic testing may be required to identify the specific gene.
MSI-H / dMMR can also indicate a good prognosis in stage 2 colon cancer, and chemotherapy may not be required in these patients.
What Immunotherapy drugs can be used in MSI-H / dMMR?
The two commonly used drugs in MSI-H / dMMR that are approved by FDA are Pembrolizumab (Keytruda) and Nivolumab (Opdyta).
Cancer Therapy India is associated with the best cancer hospital in India, having an expert team of oncologists who work together in areas of expertise to provide the highest level of patient care. We have the expertise of several specialists including surgeons, oncologists, pathologists, radiation therapists, nurses, and others to bear in customizing cancer treatment for each cancer patient.
Cancer Therapy is among the best cancer hospitals for microsatellite instability testing in Bangalore and our multidisciplinary team of experts offers molecular testing in India.
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