Comparison Between the International Standardised Approach and a Single Tube Ten Colour Flow Cytometric Assay for Detection of Minimal Residual Disease in CLL

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1460-1460
Author(s):  
Mary M Sartor ◽  
Kenneth Francis Bradstock ◽  
David Gottlieb
Keyword(s):  
Bone Marrow ◽  
Monoclonal Antibodies ◽  
Residual Disease ◽  
Excellent Correlation ◽  
Flow Cytometric Assay ◽  
Single Tube ◽  
Cell Numbers ◽  
Flow Cytometric ◽  
Colour Flow ◽  
Minimal Residual

Abstract Abstract 1460 The eradication of minimal residual disease (MRD) in CLL predicts for improved outcome. Approaches to CLL MRD detection vary in sensitivity and cost. Historically, CD5/CD19 co-expression with demonstration of clonality has been the principal method of MRD evaluation in CLL. However this approach is limited by the identification of normal hemopoietic cells and the inability to demonstrate light chain restriction with very low B cell numbers. More recently, an international standardised approach (ISA) to the assessment of MRD in CLL that utilises 10 monoclonal antibodies in a 4 tube test system and permits a sensitivity of 0.01% (Rawstron et al, Leukemia 2007) was published. Here we compare the ISA to a 10 colour flow cytometric assay incorporating all the mononclonal antibodies utilised in the ISA in a single tube. Method: Peripheral blood (n=21) and bone marrow (n=7) was collected from patients at various time points post treatment for CLL (including bone marrow from 2 patients day 30 post-allogeneic stem cell transplant). Immunophenotyping was performed using a Gallios flow cytometer (Beckman Coulter). Monoclonal antibodies were used either according to the ISA (antibody/fluorochrome combination as per Rawstron et al) or in a single tube incorporating all of the following monoclonal antibodies: CD3 ECD, CD5 PercP5.5, CD19 eFluor, CD20 PE CY7, CD81 FITC, CD22 PE, CD43 APC CY7, CD79b APC, CD38 A700, CD45 CO. A whole blood or bone marrow lyse method was used and analysis was performed according to the published ISA methodology or for the single tube using templates based on the ISA approach. Results from the two methods were compared. Results: Levels of residual disease in the 28 samples analysed varied from <0.01 to 22%. Sixteen samples showed residual disease of <1%. Analysing all samples showed an excellent correlation between the two methods slope = 0.989, intercept =0.1 and R(2)=0.992. There was also excellent correlation for disease levels below 1.0%, (median 0.03 range <0.01–0.63%, n=16) slope = 1.15, intercept =0.007 and R(2)=0.994. Bland Altman analysis showed a mean of 0.008 +/− 0.058 (2SD) for values below 1%. Conclusion: The single tube ten colour flow cytometric assay for detection of MRD in CLL gives equivalent results to the ISA. There is a potential for improved sensitivity resulting from increased event detection since there is no need to divide the sample into multiple tubes, particularly post-treatment when cell numbers are frequently limiting. The single tube assay is also simple, rapid and cost effective. Disclosures: No relevant conflicts of interest to declare.

Combined ROR1 and CD160 Detection For Improved Minimal Residual Disease In Patients With Chronic Lymphocytic Leukemia (CLL)

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2572-2572 ◽  
Author(s):  
Timothy W. Farren ◽  
Fengting Liu ◽  
Marion G. Macey ◽  
Thomas J. Kipps ◽  
Noel Warner ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Minimal Residual Disease ◽  
Research Funding ◽  
Residual Disease ◽  
Lymphocytic Leukemia ◽  
Flow Cytometric Assay ◽  
Single Tube ◽  
Flow Cytometric ◽  
Sequential Gating ◽  
Minimal Residual

Abstract Introduction Over the past decade, treatments for patients with chronic lymphocytic leukemia (CLL) have produced complete remissions (CR) without evidence for minimal residual disease (MRD), particularly for younger and/or fitter patients. In this setting, achieving an MRD-negative CR has prognostic implications, yielding longer progression free survival (PFS) and overall survival (OS) than for patients who achieve a CR with persistent MRD. Complicating efforts to incorporate testing for MRD in clinical practice has been the lack of a defined consensus on the methods of MRD detection. In this study, we report on a novel combination of mAbs for MRD detection by flow cytometry based on two antigens: the NK-cell receptor and tumor specific antigen, CD160; and the tumor associated antigen, receptor tyrosine kinase-like orphan receptor 1 (ROR-1). Objective To compare a novel single-tube, tumor-specific (CD160+ROR1) targeted approach to MRD detection against the previously published CD160 flow cytometric assay (CD160FCA) (Farren et al, 2011) and the new, single-tube 8-color ERIC assay. Methods Between October 2012 and July 2013, prospective assessment of MRD was performed on peripheral blood in 56 patients (86 samples). We developed a flow cytometric assay using mAbs specific for CD160 or ROR1 (Fukuda et al, 2008). For this we used the following mAb from BD Biosciences: CD2 FITC, CD5 Pe-Cy7, CD19 PerCP5.5, CD45V500, CD160PE, ROR-1 AF647 (“ROR-160FCA”) and a sequential gating strategy. This was compared with CD160FCA and the 8-color ERIC consortium protocol (unpublished). Light chain analysis (LCR) was performed in all cases and reported where detectable. A proof of concept spiking experiment simulating MRD was prepared by mixing CLL and normal peripheral blood leukocytes in a serial dilution to a level of 10-5(n=3). Statistical analysis was performed using Spearman Rank correlation coefficients, Mann-Whitney t-test, and Bland-Altman method comparison. Significance was set at <0.05%. Results To establish the proof of principle, MRD levels ranging from 0.001% to 100% (Neat CLL) were prepared by serial dilutions, in which MRD levels could be established by the ROR-160FCA to 10-5 (n=3). Assessment of the observed incidence against expected incidence of CLL MRD demonstrated a highly significant correlation (R2=0.96, p=0.01). In the study, the range of detectable disease went from <0.01% to 38.59%, of which 37% of samples had levels below <0.01%. Analyzing all flow cytometric methods, a highly significant correlation was observed between all three: CD160FCA vs ERIC: Spearman R=0.96 (95%CI: 0.93 - 0.97, p<0.001); CD160FCA vs ROR-160FCA: Spearman R=0.97 (95%CI: 0.96 – 0.99, p<0.001); ROR-160FCA vsERIC: Spearman R=0.97 (95%CI: 0.94 – 0.98, p<0.001). 54 samples had levels of disease <1%. Bland-Altman assay comparison in these patients again demonstrated significant associations between the assays (CD160FCA vs ERIC: mean 0.08 ±0.15; CD160FCA vs ROR-160FCA: mean 0.04 ±0.19; ROR-160FCA vs ERIC: mean 0.03 ±0.25). Light chain restriction was detectable in 24 patients (size of the restricted population ranged from 0.2% to 47% of all cellular events). This sub-group of patients also demonstrated excellent correlation between level of LCR and detectable disease by CD160FCA (Spearman R=0.96, 95%CI: 0.92-0.98, p<0.001), ERIC (R=0.95, 95%CI: 0.92-0.98, p<0.01) and ROR-160FCA (R=0.97, 95%CI 0.93-0.98, p<0.001). Conclusion Monitoring minimal residual disease in CLL is a key focus for clinical trials, as MRD is an important prognostic marker in CLL in terms of PFS and OS. Here we provide a single tube assay, ROR-160FCA, which is unique by targeting two antigens restricted to malignant B-cells, CD160 and ROR1. ROR-160FCA is equivalent in MRD detection compared to both CD160FCA and the current ERIC assay under development. The two tumor-specific antigens give ROR-160FCA the potential for improved sensitivity, particularly where limited sample is available. Furthermore, it only requires a simple sequential gating strategy, is rapid, and appears more cost effective than other Methods. References Farren TW, Giustiniani J, Liu FT et al. Blood. 2011;118 (8):2174-2183. Fukuda T, Chen L, Endo T et al. Proc Natl Acad Sci U S A. 2008;105 (8):3047-3052. Disclosures: Farren: BD Biosciences: Research Funding. Warner:BD Biosciences: Employment, Research Funding. Agrawal:BD Biosciences: Research Funding.

Improved Concordance of Minimal Residual Disease Measurements By Quantitative PCR and 10-Color Flow Cytometry in Pediatric Acute Lymphoblastic Leukemia

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2614-2614
Author(s):  
Mary Sartor ◽  
Draga Barbaric ◽  
Tamara Law ◽  
DR Anuruddhika Dissanayake ◽  
Nicola C Venn ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
Residual Disease ◽  
Rank Correlation ◽  
Color Flow ◽  
Single Tube ◽  
Time Points ◽  
Colour Flow ◽  
Risk Patients ◽  
Minimal Residual

Abstract Introduction: Detection of minimal residual disease (MRD) after induction and consolidation therapy is highly predictive of outcome for childhood acute lymphoblastic leukaemia (ALL) and is used to identify high risk patients in most current ALL clinical trials. Two methods broadly applicable for MRD analysis in ALL cases are real-time quantitative PCR based detection of unique immunoglobulin and T-cell receptor gene rearrangements (Ig/TCR PCR-MRD) and the multi-parameter flow cytometry based quantitation of Leukemia Associated Immunophenotypes (LAIP Flow-MRD). We compared the two techniques using samples from patients referred for PCR-MRD analysis initially using 4-tube 4-colour flow and more recently 1-tube 10-color flow. Methods: Newly diagnosed consented ALL patients enrolled on ANZCHOG ALL8 (2002-2011) or AIEOP-BFM ALL 2009 (2012-2014) had duplicate bone marrow aspirates, collected at diagnosis, day 15, day 33 and day 79, and analysed by PCR-MRD and Flow-MRD techniques. PCR-MRD analysis utilized clone specific primers and generic probes for Ig/TCR rearrangements according to EuroMRD guidelines. Flow-MRD which detects levels of aberrant combinations of cell-surface proteins using fluorescently labelled antibodies was performed until 2009 with 4-tube 4-colour flow before we adopted a 1-tube approach (9-colour for BCP-ALL and 10-colour T-ALL) based on the AIEOP-BFM harmonised protocol for 2012-2014. Results: Our early comparison showed a relatively poor correlation of 4-colour Flow-MRD results with PCR-MRD (Spearman rank correlation coefficient rho = 0.516, n=267) for patients enrolled at a single centre on ANZCHOG ALL8 in 2002-2009. Only the PCR-MRD results were used for the MRD risk-adapted stratification for patients on this trial. Flow-MRD for subsequent patients on this trial (2010-11) was improved by using more antibodies and adopting a single tube approach. In our current trial, day 15 Flow-MRD results are used for the early identification of low risk patients for a randomized treatment reduction. In bone marrow samples from patients enrolled on this trial, the correlation of the PCR-MRD and Flow-MRD methods is high when considered for all time points (rho = 0.803 n=418; Figure 1). In the same set of patient samples, the concordance between 2 different PCR markers based on different rearrangements was even better (rho = 0.929, n=390). A comparison of time points found that the best correlation between the two methods was observed at day 15 when MRD is often higher and the bone marrow is not regenerating (Table 1). Both PCR and 10-colour flow enabled MRD to be performed for 94% of ALL patients, and only one patient did not have a sensitive MRD assay. Conclusion: The adoption of new approaches to measurement of Flow-MRD, using a single tube and 10-colors, for ALL patients has greatly improved the concordance of Flow-MRD and PCR-MRD results. It is not surprising given the different nature of the techniques that the correlation of results produced by two different markers for PCR-MRD is higher than that with Flow. However we conclude that these two methods can now be used interchangeably at day 15 in BFM-style protocols for ALL patients. The concordance at later time points is weaker and warrants investigation in the whole trial cohort to enable effects of ALL subtype and patient outcomes to be evaluated. Table 1. Concordance of MRD levels at different time points in the same set of patients (Spearman's Rank correlation coefficient rho). MRD by PCR first Ig/TCR marker versus MRD by 10-colour flow MRD by first Ig/TCR PCR marker versus second Ig/TCR marker All timepoints 0.803 (n=418)** 0.921 (n=390)** Day 15 0.795 (n=155)** 0.950 (n=129)** Day 33 0.417 (n=137) 0.826 (n=132)** Day 79 0.383 (n=126) 0.842 (n=129)** ** Correlation is significant at the 0.01 level (2 tailed) Support: NHMRC Australia APP1057746 and Tour De Cure Foundation Figure 1. Comparison of MRD levels measured by 1-tube 10-color Flow MRD versus PCR MRD (left) or by two different PCR Ig/TCR MRD markers (right) in the 418 and 390 paired measurements in the same set of patients. Figure 1. Comparison of MRD levels measured by 1-tube 10-color Flow MRD versus PCR MRD (left) or by two different PCR Ig/TCR MRD markers (right) in the 418 and 390 paired measurements in the same set of patients. Figure 2. Figure 2. Disclosures No relevant conflicts of interest to declare.

A Single-Tube Seven-Colour Flow Cytometry Assay for Detection of Minimal Residual Disease In Myeloma.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1688-1688
Author(s):  
Soraya Wuilleme ◽  
Nelly Robillard ◽  
Steven Richebourg ◽  
Marion Eveillard ◽  
Laurence Lodé ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Plasma Cell ◽  
Plasma Cells ◽  
Residual Disease ◽  
Flow Cytometry Assay ◽  
Single Tube ◽  
Cell Identification ◽  
Colour Flow ◽  
Multiparameter Analysis ◽  
Minimal Residual

Abstract Abstract 1688 The eradication of minimal residual disease (MRD) in myeloma predicts for improved outcome. A number of different approaches to myeloma MRD detection are available; these vary widely in sensitivity and cost. Flow cytometric assessment of MRD may be preferable in practice because of lower cost and easier feasibility. Myeloma MRD flow cytometry requires at least three markers for plasma cell identification (CD38, CD138 and CD45) and combination of several additional markers to detect phenotypic abnormality including CD19, CD20, CD27, CD28, CD45, CD56 and CD117. Also, assessment of immunoglobulin light-chain restriction (cytoplasmic K and L) combined with myeloma-associated phenotypic plasma cell abnormalities, is very important. Four-tube four-colour flow cytometry combine markers CD38/CD138/CD45 with markers for plasma cell phenotypic abnormalities and clonality. Six –colour flow cytometry combines the same markers (markers for plasma cell identification) plus clonality markers; it potentially increases the sensitivity of the method through coincident multiparameter analysis. However, the single-tube six-colour flow cytometry, proposed by others studies, excludes the myeloma-associated phenotypic plasma cell abnormalities and consequently decreases specificity of the assay. We propose a new single-tube seven-colour flow cytometry, including plasma cell identification antigens, clonality markers and myeloma-associated phenotypic plasma cell abnormalities markers. In this new method, PCs are stained with antibodies: (i) CD38, CD138, CD45 used for identified plasma cells and percentage plasma cells to total leucocytes. (ii) CD19 and CD56+CD28 used to identify normal and abnormal plasma cells; and (iii) cy-IgK and cy-IgL, for confirm the plasma cells clonality. We analysed normal bone marrow provided from healthy individuals. Our results showed a presence myeloma-associated phenotypic plasma cell abnormalities at low levels in healthy individual. The monotypy studies confirm polyclonality of this normal plasma cells. Then we compared MRD assessement with single-six colour flow cytometry assay (plasma cells markers, clonality markers and exluding myeloma-associated phenotypic markers) and seven-colour flow cytometry assay (including myeloma-associated phenotypic markers). Six –colour flow cytometry has a better sensitivity and showed efficacy for quantification MRD in myeloma patients. However, the single-tube six-colour flow cytometry excluded the myeloma-associated phenotypic plasma cell abnormalities and in some cases the seven-colour flow cytometry will be more informative because it detected myeloma-asociated phenotypic marquers combined with clonality marquers. Finally, the single-tube seven colour flow cytometry assay provides reduction in antibody cost and increases sensitivity and specificity of the method through coincident multiparameter analysis. Disclosures: No relevant conflicts of interest to declare.

Augmentation of Sensitivity of FLT3/ITD Assay Allows Detection of Minimal Residual Disease In Stem Cell Transplant Recipients-Correlation with Flow Cytometric MRD Assessment

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1717-1717
Author(s):  
Maya Danielle Hughes ◽  
Rong Zeng ◽  
Kristen L. Miller ◽  
Soheil Meshinchi
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
Stem Cell ◽  
Stem Cell Transplantation ◽  
Minimal Residual Disease ◽  
Cell Transplantation ◽  
Residual Disease ◽  
Flow Cytometric ◽  
Detection Assay ◽  
Minimal Residual

Abstract Abstract 1717 FLT3 internal tandem duplication (FLT3/ITD) is a somatic mutation that is associated with therapy resistance in acute myeloid leukemia (AML). Early data demonstrated low sensitivity for this assay, thus limiting its utility to the evaluation of diagnostic specimens, and precluding its utility in remission samples. We inquired whether the standard FLT3/ITD assay can be modified to enable its utility to detect presence of residual disease in remission specimens. Enhanced FLT3/ITD assay sensitivity was accomplished by altering annealing temperature, increasing the number of cycles as well as amount and concentration of the product that was subjected to capillary electropheresis. To assess the sensitivity of the enhanced assay, FLT3/ITD positive cells M4V11 were serially diluted in a population of ITD negative cells (HL60). The concentration of M4V11 cells in each sample ranged from 10% to 0.0001%. PCR product was subjected to capillary electropheresis and the appropriate region of the electropherogram was examined for the presence of the appropriate mutant product length. Appropriate FLT3/ITD signal was detected in dilutions down to 0.01%, validating our ability to detect extremely low levels of FLT3/ITD. We subsequently examined the remission marrows from patients with a history of FLT3/ITD who had undergone stem cell transplantation. Available bone marrow specimens (N = 51) from patients who underwent stem cell transplantation for FLT3/ITD-positive AML were analyzed and the result was correlated with the available standard PCR as well as the available MRD assessment by muti-dimensional flow cytometry; samples negative for FLT3/ITD by standard assay (N=11) were then subjected to the enhanced PCR methodology. Available ITD length for each patient was used for examination of the appropriate region of the electropherogram in each case. Of the available 51 bone marrow specimens analyzed, 23 specimens had FLT3/ITD detectable by standard PCR protocol. Using our modified PCR method and capillary electrophoresis, an additional 13 specimens had identifiable FLT3/ITD. In 6/11 patients, where initial FLT3/ITD was negative by standard methodology, enhanced assay identified FLT3/ITD signal. In each case, detection of FLT3/ITD by the enhanced assay was followed by morphologic or immunophenotypic emergence of disease, prompting therapeutic intervention. We further evaluated the ability to detect FLT3/ITD in patients with minimal residual disease by flow cytometry. 33 of the bone marrow specimens analyzed had a less than 5% abnormal blast population as detectable via flow cytometry. Among these samples, 7 had FLT3/ITD detectable using standard detection techniques. An additional 11 samples had detectable FLT3/ITD when our modified protocol was employed. Of the specimens that had less than 1% abnormal blast population as detectable via flow cytometry (N = 27), 4 had FLT3/ITD detectable using the standard detection assay; when our modified protocol was employed, an additional 6 samples had detectable FLT3/ITD. 17 bone marrow specimens had no abnormal blast cells detectable via flow cytometry; of these samples 1 had detectable FLT3/ITD using the standard detection assay, while an additional 3 had detectable FLT3/ITD using our modified assay. In four patients, FLT3/ITD was detected in bone marrow specimens found to have flow cytometric MRD of 0% (N=2), 0.1% (N=1) and 0.4% (N=1). In two patients with no detectable disease by MDF, both had emergence of morphologic (60% blast) or immunophenotypic disease by MDF (1.1%) within 4–6 weeks of detection of FLT3/ITD by enhanced assay. In this study, we demonstrate that simple modifications to the FLT3/ITD genotyping assay significantly increases its sensitivity and provides a highly sensitive and very specific assay for identifying this disease associated mutation in remission specimens. The enhanced assay can be incorporated into the standard evaluation of remission status for patients with FLT3/ITD. Disclosures: No relevant conflicts of interest to declare.

Prognostic Impact of Pretransplantation Minimal Residual Disease Detection for Flow Cytometric, on Outcome of Allogeneic Hematopoietic Cell Transplantation for Acute Myeloid Leukemia. a Single Center Experience in Colombia over 14 Years

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5411-5411
Author(s):  
Andres Armando Borda Molina ◽  
Iris Cordoba ◽  
Virginia Abello ◽  
Carmen Rosales ◽  
Rosales Manuel ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Minimal Residual Disease ◽  
Myeloid Leukemia ◽  
Residual Disease ◽  
Prognostic Impact ◽  
Allogeneic Bone ◽  
Flow Cytometric ◽  
Minimal Residual ◽  
Acute Myeloid

Abstract Background: The accumulated evidence from studies of multiparameter flow cytometric MRD (MFC-MRD) assessment in AML leaves little doubt that this method of MRD detection can be used to risk stratify both younger and older patients at treatment time points. Persistence of disease or high levels of pretransplantation minimal residual disease (MRD) have been reported to predict disease relapse after Allogeneic bone marrow transplantation (BMT). The prognostic impact of MFC-MRD is strong enough to have emerged despite study differences in the MFC assays and the limitations of now outdated restricted antibody panels. Aims: To determine the value of Minimal Residual Disease (MRD) assessed by Multi-parameter Flow Cytometry (MFC) pretransplantation Allogeneic BMT, in predicting outcome in patients with acute myeloid leukemia (AML). Methods: We performed a retrospective analysis the predictive value of MRD assessment by MFC pre trasnplantation alogeneic in 119 patients (diagnosed AML treated between january 2010 and october 2014 submitted at our institution who had available MRD assessment). MRD by MFC on bone marrow specimens obtained approximately 30 days before transplantation. MRD was identified as a cell population showing deviation from normal antigen expression patters compared with normal or regenerating marrow. The detection threshold for defining pre transplantation positive MRD was >0.3%. Results - Of the 119 patients, 80 (67%) were in complete remission (CR1) , 31 (26%) CR2 and > CR2 8 (6%). Their median age was 38 years (Range, 10-64). Hyperleucocytosis in 39 (32%) and Cytogenetics was favorable risk in 32 (26%), intermediate risk in 39 (32.%), adverse risk in 35 (29%) and unknown in 13 (14%). There were a total of 44 deaths and 17 relapses; these contributed to the probability estimates for overall survival (OS) and disease free survival (DFS), stratified by MRD status and shown in figure 1. The median follow-up after BMT among survivors was 8.3 years (range, 6.9 to 9,6 years). The 7.5-years estimates of OS for MRD-positive and MRD-negative patients were 43.1% (range, 23,2% to 58,6%) and 68% (range 56% to 78.3%), respectively, and the 7,5 year estimates for DFS for MRD-positive and MRD-negative patients were 40.5% (range 21.4% to 52.6%) and 56% (range 42.5% to 65.8%). After adjustment for various covariates, age, cytogenetics risk, hyperleucocytosis, secundary AML, the hazard ratios of MRD positive versus MRD negative were 2.06 (range 1.52 to 6.24; P=0,003) for overall mortality, 3.45 ( range 2.14 to 7.32; p=0.014) for DFS. Conclusion: That detection of MRD pre transplantation define a population of patients with AML who are at higher risk for adverse outcome, even after adjusting for other factors that influence post-BMT outcome. Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

Evaluation of a 5-Color Flow Cytometric Technique for Immunophenotyping and Quantitation of Plasma Cell Myeloma in Post-Therapy Bone Marrows.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 5036-5036
Author(s):  
Tove Isaacson ◽  
Andrzej Jakubowiak ◽  
Lloyd Stoolman ◽  
Usha Kota ◽  
William Finn ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
Minimal Residual Disease ◽  
Plasma Cell ◽  
Plasma Cells ◽  
Residual Disease ◽  
Plasma Cell Myeloma ◽  
Color Flow ◽  
Flow Cytometric ◽  
Minimal Residual

Abstract Multiparameter flow cytometry is a useful tool for comprehensive immunophenotyping of plasma cell myeloma, and has been proposed as a sensitive method for the evaluation of minimal residual disease in patients following treatment. This study aimed to assess the value of flow cytometry in quantitation of residual disease, in comparison to routine morphologic examination of first-pull bone marrow aspirate smears, in myeloma patients post-therapy. Heparinized bone marrow aspirates were obtained from 27 treated patients with plasma cell myeloma. Cells were prepared for 5-color flow cytometric analysis within 24-hours of specimen draw. Surface membrane staining with anti-CD19, CD20, CD38, CD45, CD56, and CD138 was followed by ammonium chloride lysis of red cells. Fixed and permeabilized cells were analyzed for cytoplasmic light chains to confirm clonality. Data were acquired using an FC500 flow cytometer (Beckman-Coulter), analyzed with CXP software with plasma cells isolated based on bright CD38+ or CD138+ expression. A median of 97,639 cellular events (range 14,279 to 262,508) were collected per analysis. Flow cytometric enumeration of plasma cells was compared to 500-cell differential counts of Wright-Giemsa-stained first-pull aspirate smears from the same cases. The median plasma cell count as determined by flow cytometry was 0.5% (range 0–7.9%). The median plasma cell count estimated by morphologic review was 8.0% (range 0–84.4%). Flow cytometry underestimated the plasma cell content in all but one case. Clonal plasma cells expressed CD38 and CD138 in all cases; 87.5% (21/24) coexpressed CD56, 25% (6/24) coexpressed CD45, and 4.2% (1/24) coexpressed CD19. None was positive for CD20. Although detection of minimal residual disease after therapy for acute leukemia is routinely achieved by flow cytometric analysis, successful quantitation of minimal residual disease in treated myeloma patients using flow cytometry remains limited as it usually underestimates the plasma cell content of bone marrow samples compared to routine morphology of first-pull aspirates. We have observed that this holds true for both pre-treatment and post-treatment specimens. Causes for the discrepancy may include hemodilution of second-pull aspirates used for flow cytometry, fragility and loss of plasma cells during preparation for flow cytometry, and incomplete disaggregation of plasma cells from bone marrow spicules. With improved outcome of treatments, better and more reliable methods of detection of minimal residual disease are needed for optimal prognostic stratification. We are currently validating alternative methods, which may offer more sensitivity while at the same time allow more objectivity, for assessing the amount of minimal residual disease in myeloma patients.

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