Minimal residual disease (MRD) is a term used to describe the small number of cancer cells that remain in the body after cancer treatment. These cells have the potential to cause relapse in patients. MRD testing can help doctors determine how well the treatment worked, the risk of developing recurrent disease (relapse), and if further treatment is needed. MRD is used to monitor for blood and immune system cancers such as leukemia and lymphoma.
To test for MRD, doctors use samples from either a blood draw or a bone marrow biopsy. They use very sensitive methods that can find even a single cancer cell in 1 million healthy cells. These methods include flow cytometry, polymerase chain reaction (PCR), and next-generation sequencing (NGS). A positive result means that cancer cells were found in the body. A negative result means that no cancer cells were found.