In most cases, myeloma cells release monoclonal antibodies (M-protein) into your blood and urine. In rare cases, myeloma cells do not make any monoclonal antibodies, a condition called non-secretory myeloma. It can be difficult to diagnose patients with non-secretory myeloma because they have no M spike. While treatment for non-secretory myeloma is often the same as for other types of myeloma, it is more difficult to monitor treatment efficacy since doctors cannot use a simple blood test to detect the M protein.
This is an advantage of having multiple ways to measure MRD. For the clonoSEQ test, a patient needs a baseline bone marrow biopsy sample to establish the presence of an individual’s DNA sequence in the myeloma cells that can then be tracked over time. Flow cytometry does not require a baseline sample from the patient, so this is an alternative test to measure MRD if the initial bone marrow biopsy sample is not available. Flow cytometry can be used to simply count the number of myeloma cells from a recent bone marrow biopsy.
Currently there is no test that is FDA approved to measure MRD from a peripheral blood sample. There are several studies that are evaluating the use of blood-based test to measure the levels of M-proteins or circulating tumor DNA; that is a DNA fragment released by myeloma cells during cell death. Additional studies are needed to determine if a blood-based MRD test could be introduced in the clinical in the near future.
