Circulating Tumor DNA as a Detection Tool Following DLBCL Therapy | Mark Roschewski, MD | ASH 2023

My name is Mark Ruschewski. I'm a clinical investigator that works at the National Cancer Institute in Bethesda, Maryland. One of the abstracts that was presented here at the ASH meeting by myself along with collaborators was looking at the role of circulating tumor DNA to define remission at the end of therapy in patients with diffuse large piece of lymphoma who are treated with curative intent. So these are patients that have a good chance for cure when they're diagnosed and the most important time for them is at the end of therapy when they get their final PET scan to determine if they're actually in remission or not. These PET scans are excellent and crucial tests. The problem is they can be positive at the end of therapy, but patients don't actually have active lymphoma. And conversely, it can also be true that these tests are negative and up to 15% of patients will actually have a relapse somewhere down the line. So we were interested in investigating whether a blood test, this one was done by phased seek which is a highly sensitive test for circulating tumor DNA. We were interested in seeing if that could actually be a better predictor of clinical outcomes than PET scans. What we saw is that both PET scans at the end of therapy as well as these blood tests were both prognostic. But it was the blood test, the circulating tumor DNA by phased seek that was the most prognostic. It was the most predictive of who would actually progress and who wouldn't. In fact, in this series of 54 patients, no patient who tested negative at the end of therapy actually has progressed to this point. So the what we call negative predictive value or determination if someone is truly in remission was best defined by these assays of circulating tumor DNA. Alternatively, we saw that there were patients that had a negative PET scan. There were four such patients that progressed on our study and all of those patients had tested positive for MRD by circulating tumor DNA. So we envision this as a new tool that can help refine our current definition of remission and someday we will potentially be used as a formal response criteria by which we can judge the efficacy of all various therapies in lymphoma and potentially as a way to actually be a surrogate endpoint to actually get drugs approved for patients sometime in the future.