VOLUME
32
䡠
NUMBER
5
䡠
FEBRUARY
10
2014
JOURNAL OF CLINICAL ONCOLOGY
C O R R E S P O N D E N C E
Minimal Residual Disease: What Are the Minimum Requirements? TO
THE
EDITOR: Recently, Rawstron et al1 conducted a large
study that analyzed the effect of minimal residual disease (MRD) in multiple myeloma. In this large investigation, 378 patients were evaluated for MRD using multiparameter flow cytometry after induction therapy and another 397 were evaluated at day 100 after high-dose melphalan/autologous stem-cell transplantation (HDM/ASCT). An additional 245 patients were assessed for MRD after less intensive therapy. In their study, they used a 6-color antibody panel testing for CD19, CD56, CD38, CD138, CD45, and CD27 to distinguish abnormal plasma cells from normal plasma cells. They counted 500,000 cells in the bone marrow (events) and they used greater than 50 events as a cutoff for MRD positivity. Taking this approach, they had a maximum detection sensitivity of 0.01%. Overall in their study, they found that the achievement of MRD negativity was a powerful predictor of favorable outcomes. To expand our understanding regarding current MRD practices in multiple myeloma, we conducted a survey including 30 of the major medical institutions in the United States.2 Among 27 responding institutions, 15 (58%) replied that they currently do not perform MRD testing in multiple myeloma. Importantly, among 11 institutions that conduct MRD testing using multiparameter flow cytometry, we found considerable heterogeneity in methodology. This was reflected in a major difference in the antibody panel used to distinguish abnormal plasma cells from normal plasma cells. For example,
some institutions reported that they solely rely on CD19 and CD45 negativity with or without CD56 positivity to determine extent of MRD, despite evidence that normal plasma cell subpopulations can be negative for CD19 and CD45 or CD56 positive.3,4 Only a few institutions used specific antigens such as CD81 and CD117. Furthermore, we found a major discordance in the number of events and the cut-offs for MRD positivity. Indeed, the number of events counted varied from 100,000 to 4,000,000, with most institutions obtaining between 100,000 to 500,000 events (Table 1). Similarly, the number of abnormal plasma cells needed to define MRD positivity ranged from 20 to 50 (Table 1). This translated into a maximum detection sensitivity ranging from 0.0005% to 0.02%—a 100-fold difference. In the setting of HDM/ASCT, the achievement of a complete response or very good partial response is associated with improved progression-free and overall survival,5-7 but questions remain if the benefit of a deep response is a result of biologic features, patient characteristics, treatment delivered, or a combination. Some reports suggest that this benefit is strongest in high-risk subgroups.8,9 Paiva et al10 first demonstrated that MRD detected by multicolor flow cytometry predicted a higher risk for relapse in patients who achieved complete response after HDM/ASCT. In patients treated without HDM/ ASCT, the same group demonstrated that multicolor flow cytometry similarly provided more prognostic information after initial therapy than serum immunoelectropheresis and free light chains.11 We believe that MRD testing will become increasingly important in multiple myeloma as modern therapies continue to evolve with better and deeper responses achieved.12-14 In our opinion, we urgently need to define consensus criteria for the minimum requirement for
Table 1. Flow Cytometry of the Bone Marrow to Detect MRD in Multiple Myeloma: Current Practice Based on a Survey of 30 Major Institutions in the United States
Institution
No. of Events Acquired in MRD Testing
Minimum No. of Abnormal Plasma Cells Needed to Call MRD
1 2 3 4 5 6 7 8 9 10 11 Rawstron1
3,000,000-4,000,000 1,800,000 1,000,000 500,000 500,000 300,000-500,000 250,000-500,000 100,000 100,000 Variable N/A 100,000-500,000
20 50 50 25 N/A 30-35 50 20 Variable† 20 30 50
Maximum Possible Sensitivityⴱ
No. of Antigens Studied
0.0005% 0.003% 0.005% 0.005%
12 9 8 6 8 8 10 10 8 8 8 6
0.006% 0.01% 0.02% N/A N/A N/A 0.01%
NOTE. Table adapted from Flanders et al.2 Thirty institutions in the United States were surveyed regarding institutional protocols for the assessment of MRD with flow cytometry after therapy for multiple myeloma. Twenty-seven institutions responded, with 11 providing details on their collection methods. Above are the 11 institutions’ responses in addition to the methods described by Rawstron et al.1 Abbreviations: MRD, minimal residual disease; N/A, not available. ⴱ Maximum possible sensitivity determined by dividing the minimum number of abnormal plasma cells needs to call MRD by the number of events acquired in MRD testing (i.e. a lower percentage indicates a more sensitive approach). For institutions with a range, the lowest number of minimum abnormal plasma cells needed and the highest number of events acquired were used for the calculation. †Dependent on the pathologist.
Journal of Clinical Oncology, Vol 32, No 5 (February 10), 2014: pp 475-485
© 2014 by American Society of Clinical Oncology
Information downloaded from jco.ascopubs.org and provided by at Gazi Universitesi on October 4, 2014 from 194.27.18.18 Copyright © 2014 American Society of Clinical Oncology. All rights reserved.
475
Correspondence
MRD testing in multiple myeloma. Also, we need to clarify the optimal timing for MRD testing to better allow comparison across studies. Coordinated and collaborative efforts are needed to move MRD testing in multiple myeloma forward and to implement this terminology in treatment trials as well as in clinical practice.
Mark Roschewski, Maryalice Stetler-Stevenson, Constance Yuan, Sham Mailankody, Neha Korde, and Ola Landgren Center for Cancer Research, National Institutes of Health, Bethesda, MD
AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST
The author(s) indicated no potential conflicts of interest. REFERENCES 1. Rawstron AC, Child JA, de Tute RM, et al: Minimal residual disease assessed by multiparameter flow cytometry in multiple myeloma: Impact on outcome in the Medical Research Council Myeloma IX Study. J Clin Oncol 31:2540-2547, 2013 2. Flanders A, Stetler-Stevenson M, Landgren O: Minimal residual disease testing in multiple myeloma by flow cytometry: Major heterogeneity. Blood 122:1088-1089, 2013 3. Liu D, Lin P, Hu Y, et al: Immunophenotypic heterogeneity of normal plasma cells: Comparison with minimal residual plasma cell myeloma. J Clin Pathol 65:823-829, 2012 4. Cannizzo E, Bellio E, Sohani AR, et al: Multiparameter immunophenotyping by flow cytometry in multiple myeloma: The diagnostic utility of defining ranges of normal antigenic expression in comparison to histology. Cytometry B Clin Cytom 78:231-238, 2010 5. van de Velde HJ, Liu X, Chen G, et al: Complete response correlates with long-term survival and progression-free survival in high-dose therapy in multiple myeloma. Haematologica 92:1399-1406, 2007
6. Martinez-Lopez J, Blade J, Mateos MV, et al: Long-term prognostic significance of response in multiple myeloma after stem cell transplantation. Blood 118:529-534, 2011 7. Lahuerta JJ, Mateos MV, Martinez-Lo´pez J, et al: Influence of pre- and post-transplantation responses on outcome of patients with multiple myeloma: Sequential improvement of response and achievement of complete response are associated with longer survival. J Clin Oncol 26:5775-5782, 2008 8. Haessler J, Shaughnessy JD, Zhan F, et al: Benefit of complete response in multiple myeloma limited to high-risk subgroup identified by gene expression profiling. Clin Cancer Res 13:7073-7079, 2007 9. Hoering A, Crowley J, Shaughnessy JD Jr, et al: Complete remission in multiple myeloma examined as time-dependent variable in terms of both onset and duration in Total Therapy protocols. Blood 114:1299-1305, 2009 10. Paiva B, Vidriales MB, Cervero´ J, et al: Multiparameter flow cytometric remission is the most relevant prognostic factor for multiple myeloma patients who undergo autologous stem cell transplantation. Blood 112:40174023, 2008 11. Paiva B, Martinez-Lopez J, Vidriales MB, et al: Comparison of immunofixation, serum free light chain, and immunophenotyping for response evaluation and prognostication in multiple myeloma. J Clin Oncol 29:1627-1633, 2011 12. Jakubowiak AJ, Dytfeld D, Griffith KA, et al: A phase 1/2 study of carfilzomib in combination with lenalidomide and low-dose dexamethasone as a frontline treatment for multiple myeloma. Blood 120:1801-1809, 2012 13. Korde N, Zingone A, Kwok M, et al: Phase II clinical and correlative study of carfilzomib, lenalidomide, and dexamethasone (CRd) in newly diagnosed multiple myeloma (MM) patients. ASH Annual Meeting Abstracts 120:732, 2012 14. Richardson PG, Weller E, Lonial S, et al: Lenalidomide, bortezomib, and dexamethasone combination therapy in patients with newly diagnosed multiple myeloma. Blood 116:679-686, 2010
DOI: 10.1200/JCO.2013.52.1955; published online ahead of print at www.jco.org on January 13, 2014
■ ■ ■
Reply to M. Roschewski et al We agree with Roschewski et al1 at the National Institutes of Health that minimal residual disease (MRD) assessment has become increasingly important in multiple myeloma (MM). Several key points have emerged from our studies2,3 and those of colleagues at the University of Salamanca (Salamanca, Spain).4-6 Namely that MRD assessment by flow cytometry is predictive of outcome in patients treated with both autologous stem-cell transplantation (ASCT) and non-ASCT containing schedules and is applicable to patients with both adverse and standard-risk cytogenetic profiles. Importantly, MRD assesment predicts outcome in patients achieving conventional complete response and is a useful tool in assessing the merits of individual elements of complex multicomponent therapy when sequential changes in M protein concentrations can be misleading or uninformative. Roschewski et al1 also, correctly in our view, raise concerns regarding heterogeneity in methodology, which is highlighted in their recent survey of US centers.7 We agree that there is a need to define consensus criteria for the minimum requirements for MRD testing in MM. Experience of residual disease monitoring in other disorders has reinforced the need to use a quantitative assay to ensure that different approaches used in different clinical trials can be directly compared, identify harmonized approaches with identification of the minimum requirements for a suitable assay, and maintain flexibility in the assay design and technology platform so that scientific advances can be used to improve the ease and cost of analysis. 476
© 2014 by American Society of Clinical Oncology
The first two studies to demonstrate an increased relapse risk associated with MRD after ASCT were reported more than a decade ago, and in both studies, the limit of detection was 0.01%.2,8 Since then, there have been major improvements in both flow cytometry and molecular biology, which could permit MRD detection with greater sensitivity, but so far the 0.01% threshold has consistently demonstrated prognostic relevance.2-6,8,9 With flow cytometry assays the limit of detection will depend on the number of events used to define a population as well as the total number of events acquired. This limit of detection is only reproducible if the assay contains sufficient antigens to reliably discriminate the neoplastic cells in virtually all cases. The dilute nature of many post-treatment marrow samples is also a factor to consider. Acquiring a large number of events may potentially improve the sensitivity and limit of quantification but aiming for a larger volume of marrow to obtain sufficient cells can be counterproductive because of greater hemodilution. This may paradoxically underestimate the residual disease level. This limitation will apply to any technique, irrespective of its potential sensitivity, that requires a representative bone marrow sample (as opposed to serum or whole blood). Regarding the minimum number of events required to define MRD, our experience is that 10 or 20 events is often sufficient but is poorly reproducible when different operators analyze the same data, and at least 50 events are required for good interlaboratory reproducibility.10,11 The analysis of more antigens may be helpful, but if this requires additional independent tubes, then it may limit sensitivity in some cases. Previous harmonization efforts have demonstrated that three markers JOURNAL OF CLINICAL ONCOLOGY
Information downloaded from jco.ascopubs.org and provided by at Gazi Universitesi on October 4, 2014 from 194.27.18.18 Copyright © 2014 American Society of Clinical Oncology. All rights reserved.
32
䡠
NUMBER
5
䡠
FEBRUARY
10
2014
JOURNAL OF CLINICAL ONCOLOGY
C O R R E S P O N D E N C E
Minimal Residual Disease: What Are the Minimum Requirements? TO
THE
EDITOR: Recently, Rawstron et al1 conducted a large
study that analyzed the effect of minimal residual disease (MRD) in multiple myeloma. In this large investigation, 378 patients were evaluated for MRD using multiparameter flow cytometry after induction therapy and another 397 were evaluated at day 100 after high-dose melphalan/autologous stem-cell transplantation (HDM/ASCT). An additional 245 patients were assessed for MRD after less intensive therapy. In their study, they used a 6-color antibody panel testing for CD19, CD56, CD38, CD138, CD45, and CD27 to distinguish abnormal plasma cells from normal plasma cells. They counted 500,000 cells in the bone marrow (events) and they used greater than 50 events as a cutoff for MRD positivity. Taking this approach, they had a maximum detection sensitivity of 0.01%. Overall in their study, they found that the achievement of MRD negativity was a powerful predictor of favorable outcomes. To expand our understanding regarding current MRD practices in multiple myeloma, we conducted a survey including 30 of the major medical institutions in the United States.2 Among 27 responding institutions, 15 (58%) replied that they currently do not perform MRD testing in multiple myeloma. Importantly, among 11 institutions that conduct MRD testing using multiparameter flow cytometry, we found considerable heterogeneity in methodology. This was reflected in a major difference in the antibody panel used to distinguish abnormal plasma cells from normal plasma cells. For example,
some institutions reported that they solely rely on CD19 and CD45 negativity with or without CD56 positivity to determine extent of MRD, despite evidence that normal plasma cell subpopulations can be negative for CD19 and CD45 or CD56 positive.3,4 Only a few institutions used specific antigens such as CD81 and CD117. Furthermore, we found a major discordance in the number of events and the cut-offs for MRD positivity. Indeed, the number of events counted varied from 100,000 to 4,000,000, with most institutions obtaining between 100,000 to 500,000 events (Table 1). Similarly, the number of abnormal plasma cells needed to define MRD positivity ranged from 20 to 50 (Table 1). This translated into a maximum detection sensitivity ranging from 0.0005% to 0.02%—a 100-fold difference. In the setting of HDM/ASCT, the achievement of a complete response or very good partial response is associated with improved progression-free and overall survival,5-7 but questions remain if the benefit of a deep response is a result of biologic features, patient characteristics, treatment delivered, or a combination. Some reports suggest that this benefit is strongest in high-risk subgroups.8,9 Paiva et al10 first demonstrated that MRD detected by multicolor flow cytometry predicted a higher risk for relapse in patients who achieved complete response after HDM/ASCT. In patients treated without HDM/ ASCT, the same group demonstrated that multicolor flow cytometry similarly provided more prognostic information after initial therapy than serum immunoelectropheresis and free light chains.11 We believe that MRD testing will become increasingly important in multiple myeloma as modern therapies continue to evolve with better and deeper responses achieved.12-14 In our opinion, we urgently need to define consensus criteria for the minimum requirement for
Table 1. Flow Cytometry of the Bone Marrow to Detect MRD in Multiple Myeloma: Current Practice Based on a Survey of 30 Major Institutions in the United States
Institution
No. of Events Acquired in MRD Testing
Minimum No. of Abnormal Plasma Cells Needed to Call MRD
1 2 3 4 5 6 7 8 9 10 11 Rawstron1
3,000,000-4,000,000 1,800,000 1,000,000 500,000 500,000 300,000-500,000 250,000-500,000 100,000 100,000 Variable N/A 100,000-500,000
20 50 50 25 N/A 30-35 50 20 Variable† 20 30 50
Maximum Possible Sensitivityⴱ
No. of Antigens Studied
0.0005% 0.003% 0.005% 0.005%
12 9 8 6 8 8 10 10 8 8 8 6
0.006% 0.01% 0.02% N/A N/A N/A 0.01%
NOTE. Table adapted from Flanders et al.2 Thirty institutions in the United States were surveyed regarding institutional protocols for the assessment of MRD with flow cytometry after therapy for multiple myeloma. Twenty-seven institutions responded, with 11 providing details on their collection methods. Above are the 11 institutions’ responses in addition to the methods described by Rawstron et al.1 Abbreviations: MRD, minimal residual disease; N/A, not available. ⴱ Maximum possible sensitivity determined by dividing the minimum number of abnormal plasma cells needs to call MRD by the number of events acquired in MRD testing (i.e. a lower percentage indicates a more sensitive approach). For institutions with a range, the lowest number of minimum abnormal plasma cells needed and the highest number of events acquired were used for the calculation. †Dependent on the pathologist.
Journal of Clinical Oncology, Vol 32, No 5 (February 10), 2014: pp 475-485
© 2014 by American Society of Clinical Oncology
Information downloaded from jco.ascopubs.org and provided by at Gazi Universitesi on October 4, 2014 from 194.27.18.18 Copyright © 2014 American Society of Clinical Oncology. All rights reserved.
475
Correspondence
MRD testing in multiple myeloma. Also, we need to clarify the optimal timing for MRD testing to better allow comparison across studies. Coordinated and collaborative efforts are needed to move MRD testing in multiple myeloma forward and to implement this terminology in treatment trials as well as in clinical practice.
Mark Roschewski, Maryalice Stetler-Stevenson, Constance Yuan, Sham Mailankody, Neha Korde, and Ola Landgren Center for Cancer Research, National Institutes of Health, Bethesda, MD
AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST
The author(s) indicated no potential conflicts of interest. REFERENCES 1. Rawstron AC, Child JA, de Tute RM, et al: Minimal residual disease assessed by multiparameter flow cytometry in multiple myeloma: Impact on outcome in the Medical Research Council Myeloma IX Study. J Clin Oncol 31:2540-2547, 2013 2. Flanders A, Stetler-Stevenson M, Landgren O: Minimal residual disease testing in multiple myeloma by flow cytometry: Major heterogeneity. Blood 122:1088-1089, 2013 3. Liu D, Lin P, Hu Y, et al: Immunophenotypic heterogeneity of normal plasma cells: Comparison with minimal residual plasma cell myeloma. J Clin Pathol 65:823-829, 2012 4. Cannizzo E, Bellio E, Sohani AR, et al: Multiparameter immunophenotyping by flow cytometry in multiple myeloma: The diagnostic utility of defining ranges of normal antigenic expression in comparison to histology. Cytometry B Clin Cytom 78:231-238, 2010 5. van de Velde HJ, Liu X, Chen G, et al: Complete response correlates with long-term survival and progression-free survival in high-dose therapy in multiple myeloma. Haematologica 92:1399-1406, 2007
6. Martinez-Lopez J, Blade J, Mateos MV, et al: Long-term prognostic significance of response in multiple myeloma after stem cell transplantation. Blood 118:529-534, 2011 7. Lahuerta JJ, Mateos MV, Martinez-Lo´pez J, et al: Influence of pre- and post-transplantation responses on outcome of patients with multiple myeloma: Sequential improvement of response and achievement of complete response are associated with longer survival. J Clin Oncol 26:5775-5782, 2008 8. Haessler J, Shaughnessy JD, Zhan F, et al: Benefit of complete response in multiple myeloma limited to high-risk subgroup identified by gene expression profiling. Clin Cancer Res 13:7073-7079, 2007 9. Hoering A, Crowley J, Shaughnessy JD Jr, et al: Complete remission in multiple myeloma examined as time-dependent variable in terms of both onset and duration in Total Therapy protocols. Blood 114:1299-1305, 2009 10. Paiva B, Vidriales MB, Cervero´ J, et al: Multiparameter flow cytometric remission is the most relevant prognostic factor for multiple myeloma patients who undergo autologous stem cell transplantation. Blood 112:40174023, 2008 11. Paiva B, Martinez-Lopez J, Vidriales MB, et al: Comparison of immunofixation, serum free light chain, and immunophenotyping for response evaluation and prognostication in multiple myeloma. J Clin Oncol 29:1627-1633, 2011 12. Jakubowiak AJ, Dytfeld D, Griffith KA, et al: A phase 1/2 study of carfilzomib in combination with lenalidomide and low-dose dexamethasone as a frontline treatment for multiple myeloma. Blood 120:1801-1809, 2012 13. Korde N, Zingone A, Kwok M, et al: Phase II clinical and correlative study of carfilzomib, lenalidomide, and dexamethasone (CRd) in newly diagnosed multiple myeloma (MM) patients. ASH Annual Meeting Abstracts 120:732, 2012 14. Richardson PG, Weller E, Lonial S, et al: Lenalidomide, bortezomib, and dexamethasone combination therapy in patients with newly diagnosed multiple myeloma. Blood 116:679-686, 2010
DOI: 10.1200/JCO.2013.52.1955; published online ahead of print at www.jco.org on January 13, 2014
■ ■ ■
Reply to M. Roschewski et al We agree with Roschewski et al1 at the National Institutes of Health that minimal residual disease (MRD) assessment has become increasingly important in multiple myeloma (MM). Several key points have emerged from our studies2,3 and those of colleagues at the University of Salamanca (Salamanca, Spain).4-6 Namely that MRD assessment by flow cytometry is predictive of outcome in patients treated with both autologous stem-cell transplantation (ASCT) and non-ASCT containing schedules and is applicable to patients with both adverse and standard-risk cytogenetic profiles. Importantly, MRD assesment predicts outcome in patients achieving conventional complete response and is a useful tool in assessing the merits of individual elements of complex multicomponent therapy when sequential changes in M protein concentrations can be misleading or uninformative. Roschewski et al1 also, correctly in our view, raise concerns regarding heterogeneity in methodology, which is highlighted in their recent survey of US centers.7 We agree that there is a need to define consensus criteria for the minimum requirements for MRD testing in MM. Experience of residual disease monitoring in other disorders has reinforced the need to use a quantitative assay to ensure that different approaches used in different clinical trials can be directly compared, identify harmonized approaches with identification of the minimum requirements for a suitable assay, and maintain flexibility in the assay design and technology platform so that scientific advances can be used to improve the ease and cost of analysis. 476
© 2014 by American Society of Clinical Oncology
The first two studies to demonstrate an increased relapse risk associated with MRD after ASCT were reported more than a decade ago, and in both studies, the limit of detection was 0.01%.2,8 Since then, there have been major improvements in both flow cytometry and molecular biology, which could permit MRD detection with greater sensitivity, but so far the 0.01% threshold has consistently demonstrated prognostic relevance.2-6,8,9 With flow cytometry assays the limit of detection will depend on the number of events used to define a population as well as the total number of events acquired. This limit of detection is only reproducible if the assay contains sufficient antigens to reliably discriminate the neoplastic cells in virtually all cases. The dilute nature of many post-treatment marrow samples is also a factor to consider. Acquiring a large number of events may potentially improve the sensitivity and limit of quantification but aiming for a larger volume of marrow to obtain sufficient cells can be counterproductive because of greater hemodilution. This may paradoxically underestimate the residual disease level. This limitation will apply to any technique, irrespective of its potential sensitivity, that requires a representative bone marrow sample (as opposed to serum or whole blood). Regarding the minimum number of events required to define MRD, our experience is that 10 or 20 events is often sufficient but is poorly reproducible when different operators analyze the same data, and at least 50 events are required for good interlaboratory reproducibility.10,11 The analysis of more antigens may be helpful, but if this requires additional independent tubes, then it may limit sensitivity in some cases. Previous harmonization efforts have demonstrated that three markers JOURNAL OF CLINICAL ONCOLOGY
Information downloaded from jco.ascopubs.org and provided by at Gazi Universitesi on October 4, 2014 from 194.27.18.18 Copyright © 2014 American Society of Clinical Oncology. All rights reserved.
