Once you begin myeloma therapy, how do you know if it’s working? Dr. Saad Usmani, a myeloma expert, shares how patients are monitored via various tests and reviews how minimal residual disease (MRD) testing plays a role in myeloma care.
Dr. Saad Usmani is the Chief of Myeloma Service at Memorial Sloan Kettering Cancer Center in New York City. Learn more about Dr. Usmani, here.
Once a patient begins therapy, how do you monitor whether a treatment is working?
So, as part of the diagnostic work-up, we typically have identified in the blood using serum protein electrophoresis and serum free light chains. What kind of myeloma proteins these – that particular patient’s myeloma cells are making. And we can monitor them every cycle of treatment. So, every three or four weeks.
And that’s the most noninvasive way of seeing if the treatment is working. The second obviously important thing is if someone has symptoms. If they have kidney damage, if they have bone pain, all of those things start improving as you’re getting treatment. And then in some patients, we’re also looking at imaging like PET CT scans at certain time points. And at some point, we do also look at the bone marrow biopsies to see what’s really going on in the factory.
We often hear the term MRD, or minimal residual disease used in the myeloma space. So, what is it exactly and how is it used in patient care?
So, minimal residual disease is a way to measure how much myeloma is left over in a given patient.
And historically, we were simply looking at the serum proteins and the light chain levels along with just the morphology of the bone marrow to see if – kind of determine a response. But we can have a much deeper assessment of how many cancer cells as a leftover from a bone marrow biopsy by different measurements. Someone can be in a complete response with M-Spike is gone. The light chains have normalized.
Yet they can still have 10,000 – 100,000 myeloma cells still in the bone marrow. And just using the bone marrow biopsy the way that we used to, we won’t be able to see them. We’ll just see, “Oh, these look like normal plasma cells.” So, using next-generation sequencing and flow cytometry, we can look at normal myeloma cells at a very deep level – one out of one million.
But these tests are highly specialized. And especially the flow cytometry requires a lot of expertise. The NGS requires good sampling at the time of diagnosis as well as subsequent specimen