NEW YORK – Evidence of minimal residual disease (MRD) has been shown to be an important prognostic factor in several different hematologic malignancies, including acute and chronic myeloid leukemias, but its clinical utility in day-to-day practice in multiple myeloma is still uncertain.
At the annual Lymphoma & Myeloma International Congress on Hematologic Malignancies, C. Ola Landgren, MD, PhD, chief of the myeloma service at Memorial Sloan Kettering Cancer Center in New York, and Paul G. Richardson, MD, clinical program leader and director of clinical research at the Jerome Lipper Myeloma Center at the Dana-Farber Cancer Institute in Boston, debated the question: “Is MRD ready for prime time?”
Yes: Dr. Landgren
“As we all know, with older drugs for myeloma, only a small proportion of patients reached a complete response, so there was really no reason to talk about MRD. But this belongs to the past: using the modern combination therapies, about 100% of our patients have a response, an overall response, and up to 80% of patients are reaching a complete response. So it’s really necessary, a logical step to go forward, to look at MRD,” Dr. Landgren said.
He cited evidence from two meta-analyses showing that MRD negativity is a strong predictor of clinical outcomes, including long-term survival.
Dr. C. Ola Landgren
“Our results show that MRD negativity is a strong predictor of clinical outcomes, supportive of MRD becoming a regulatory end point for drug approval in newly diagnosed multiple myeloma,” they wrote.
In a second meta-analysis, Nikhil Munshi, MD, from the Dana-Farber Cancer Institute, and his colleagues, reviewed PFS data from 14 studies with a total of 1,273 patients, and OS data from 12 studies with a total of 1,100 patients.
This second meta-analysis found that MRD negativity was associated with significantly better PFS (HR, 0.41; P less than .001), including among patients in studies looking specifically at complete response (CR) (HR, 0.44; P less than .001).
Munshi et al. also saw a significant benefit for MRD negativity among all patients in trials with OS as the endpoint (HR, 0.57; P less than .001) and in those focusing on patients with a CR (HR, 0.47; P less than .001).
They concluded that MRD-negative status after treatment for new newly diagnosed multiple myeloma is associated with long-term survival, and like Landgren et al. contended that their findings “provide quantitative evidence to support the integration of MRD assessment as an end point in clinical trials of multiple myeloma.”
Dr. Landgren noted that 2016 International Myeloma Working Group consensus criteria for response and minimal residual disease assessment in multiple myeloma, coauthored by both Dr. Landgren and Dr. Richardson, now incorporate MRD.
In addition, in the IFM/DFCI 2009 trial comparing induction therapy for patients with newly diagnosed multiple myeloma with or without autologous stem cell transplant after three cycles of lenalidomide, bortezomib, and dexamethasone, patients in each trial arm who were MRD negative had significantly better PFS than patients who were MRD positive after consolidation, regardless of assigned treatment, Dr. Landgren noted.
In the relapsed/refractory multiple myeloma setting, MRD negativity was associated with better PFS for patients in the POLLUX trial, whether subjects were assigned to receive daratumumab plus lenalidomide and dexamethasone, or len-dex alone.
“This raises an important question: Is MRD more important than treatment modality?” Dr. Landgren said.
“The debate is: Is MRD ready for prime time? And as I have shown you with all the data, the answer is ‘Yes’,” he concluded.
No: Dr. Richardson
“My position on this is that MRD testing is absolutely ready for prime time in the research and regulatory arena. The question for me as a clinician in my clinic is: ‘Do I apply it to everyday practice?’ And I would simply suggest to you at this point we’re not ready for that, and we’re not ready for that for a variety of complex reasons,” Dr. Richardson said in his rebuttal.
He cited a definition of MRD offered by Simone Ferrero, MD, and his colleagues from the University of Turin (Italy) in 2011 in Hematological Oncology: “Any approach aimed at detecting and possibly quantifying residual tumor cells beyond the sensitivity level of routine imaging and laboratory techniques.”
Dr. Paul G. Richardson
“We recognize in hematologic malignancies in particular, and increasingly in myeloma, that achievement of complete clinical remission and assessing this needs a variety of different scenarios,” he said.
These scenarios may include establishing the full eradication of the neoplastic clone, determining the long-term persistence of quiescent or nonclonogenic or immunologically regulated tumor cells, or persistence of clonogenic cells capable of giving rise to a full clinical relapse within a number of years.
Myeloma specialists recognize that MRD is a real phenomenon, made more challenging by the “extraordinary” heterogeneity of myeloma, he said.
Determination of MRD using sensitive molecular techniques may allow analysis of treatments that induce a greater depth of response than others, and may also identify patients who are experiencing early relapse and will need further treatment, Dr. Richardson acknowledged.
“The question is, should it dictate what you and I do every afternoon in the clinic with a particular patient, for example, outside of a clinical trial?”
He noted that MRD is still a secondary endpoint in trials for acute lymphoblastic leukemia, acute myeloid leukemia, acute promyelocytic leukemia, and chronic lymphocytic leukemia, although it has been accepted by the FDA as a primary endpoint to assess molecular responses to second-generation tyrosine kinase inhibitors.
MRD is also still a secondary endpoint in trials for therapies against follicular and mantle cell lymphomas as well.
“So my hypothesis, or suggestion to you this morning, is that whilst MRD clearly is a vital area of research – and I especially applaud Ola for being on the forefront of this, and I fully support all the points he made – I would just simply suggest to you that it’s less advanced than in leukemia and lymphoma, and we are currently at the point where MRD assessments are clearly secondary endpoints and an important research tool,” he said,
MRD remains a research tool in multiple myeloma because, despite the wealth of new therapies and combinations approved in just the past few years, “we’re not able to eradicate it completely, and cure remains in myeloma, frankly, evasive,” he added.
Immunotherapy, for example, is not the “mutationally agnostic” approach that clinicians had hoped for, with recent evidence suggesting that it cannot overcome every genetic variation that may give rise to multiple myeloma.
For MRD to become a useful clinical tool rather than a research/regulatory tool, standardization of testing methods will be needed. Flow cytometry until recently has been the mainstay for detecting MRD, but molecular strategies are currently being investigated, and rapid next-generation sequencing has the potential to become a gold standard, with its ability to identify and quantify all clonotypes in a sample.
“What’s critical is, therapeutic adjustment for what? What is the difference? For example, [if] one arm of a trial has 20% MRD positivity vs. 40% in another, what does that really mean for overall survival? These are enormous challenges that we still face,” Dr. Richardson said.
“I do think the lack of standardization broadly across the country is a challenge, and so with that in mind, I would simply suggest that it is not yet a standard of care in clinical practice, but may be,” he concluded.
Dr. Landgren disclosed serving as a consultant to AbbVie, Amgen, Bristol-Myers Squibb, Celgene and Janssen. Dr. Richardson disclosed consulting for Celgene and Takeda.