Paola Ghione, MD
Dr. Ghione is a visiting hematology fellow from Torino, Italy who is working with the Weill Cornell Lymphoma Program for six months.
Minimal residual disease (MRD) detection refers to a group of techniques used to find a very small amount of disease, normally undetectable with imaging or clinical exam. Usually, this detection is performed after treatment and, in many cases, is predictive of outcomes such as whether patients will relapse, and how quickly this might happen. Often, the reappearance of MRD can anticipate recurrence of lymphoma before it becomes clinically evident. In other hematologic disorders, such as acute leukemia and chronic myeloid leukemia, MRD is used in standard clinical practice to monitor disease status or to evaluate response to treatment. In the setting of lymphoma, measurement of MRD is still considered experimental, but a lot of research is taking place around the world to find the best way to perform it.
Our laboratory in Torino, Italy, run by Dr. Marco Ladetto and Dr. Simone Ferrero, leads many MRD projects for lymphoma and is part of the EuroMRD Network, an institution born in Europe to standardize MRD techniques. Currently, we look for tumor-specific DNA alterations in the blood before and after treatment using a technique called Allele-Specific Oligonucleotide (ASO)-PCR. Depending on how much tumor DNA is present in the blood, we can figure out the relative amount of tumor left in the body. Unfortunately, ASO-PCR requires an expert laboratory team, and the method is expensive and time-consuming, which makes it hard to use outside of specialized settings. In addition, it seems more reliable if performed directly on bone marrow aspirate (blood from the interior of the bone) than peripheral blood (coming from a normal vein), making it less attractive to clinicians and people with lymphoma.
New techniques that can speed the procedure and reduce the cost are being evaluated. For example, the droplet digital (dd)-PCR is interesting because it is faster and uses less material (i.e., requires less blood for the test). Another interesting method is Next Generation Sequencing (NGS), which allows the detection of several different DNA mutations at once. NGS analysis of cell-free circulating DNA(cfDNA) (the DNA present in circulating blood outside the cells) could give a lot information. Studying cfDNA from the blood could give us a more accurate picture of the lymphoma that in theory could be even better than studying DNA derived from an open biopsy at one site of disease. This is also sometimes referred to as a liquid biopsy. The reason it might be better is that the circulating cfDNA could show us mutations coming from all the sites where the tumor is actively growing, not only the one site from which the open biopsy is taken.
In Italy, although MRD is not yet available in routine clinical practice for treating lymphoma, it is being tested in some innovative clinical trials to guide treatment decisions. In some studies MRD negativity at the end of treatment is the primary goal, while in others reappearance of MRD prompts a preemptive approach. As an example, if MRD reappears when the person is off therapy, we can give a short re-treatment in order to avoid clinical relapse. In one of our clinical trials, evaluation of MRD has been used to rule out the presence of lymphoma in the cells collected prior to autologous stem cell transplantation.
Measurement of MRD has a lot of potential uses, and experience from other diseases proves that it can be practice changing. The challenges provided by more than 50 different lymphoma subtypes as well as the rapid evolution of new laboratory techniques have delayed the adoption of a universal test for MRD. In the near future, however, we expect to see MRD analysis in standard clinical practice everywhere.