Prognostic relevance of cytometric quantitative assessment in patients with myelodysplastic syndromes

The flow cytometry myeloid progenitor count: A reproducible parameter for diagnosis and prognosis of myelodysplastic syndromes

BACKGROUND

The bone marrow blast count is central to the diagnosis and monitoring of myelodysplastic syndromes (MDS). It is an independent risk factor for worse prognosis whether based on the morphology blast count or the flow cytometry (FC) myeloid progenitor (MyP) count. It is a principal population in FC MDS analysis also because once defined; it provides significant contributions to the overall FC MDS score.

METHODS

We elected to investigate inter-analyst agreement for the most fundamental parameter of the FC MDS diagnostic score: the MyP count. A common gating strategy was agreed and used by seven cytometrists for blind analysis of 34 routine bone marrows sent for MDS work-up. Additionally, we compared the results with a computational approach.

RESULTS

Concordance was excellent: Intraclass correlation was 0.993 whether measuring %MyP of total cells or CD45+ cells, and no significant difference was observed between files from different centers or for samples with abnormal MyP phenotypes. Computational and manual results were similar. Applying the common strategy to individual laboratories' control cohorts produced similar MyP reference ranges across centers.

CONCLUSION

The FC MyP count offers a reliable diagnostic and prognostic measurement in MDS. The use of manual and computational approaches side by side may allow for optimizing both strategies. Considering its known prognostic power, the MyP count could be considered a useful and reliable addition to existing prognostic scoring systems.

The utility of a single tube 10-color flow cytometry for quantitative and qualitative analysis in myelodysplastic syndrome- a pilot study

INTRODUCTION

Assessment of myelodysplasia (MDS) by flow cytometry (FCM) includes elaborate panels, and interpretation is observer-dependent. This study evaluates single tube 10-color FCM in a test cohort of clinically suspected MDS patients.

METHODS

We analyzed fifty-six bone marrow (BM) samples from clinically suspected MDS patients in a morphology-blinded manner along with controls using a 10-color single tube flow cytometry. We analyzed the reproducibility of Ogata score and modified FCM scores, additionally incorporating the proportion of CD15, CD11b, CD56, and CD38MFI on CD34+CD19-cluster for each patient. Patients were grouped as proven-MDS, suspected-MDS, and non-MDS groups based on morphology and cytogenetics. Optimized multi-axial radar-plots were also used to analyze maturation patterns in the granulocytic, monocytic, and blast progenitor compartments of proven-MDS cases and controls.

RESULTS

Flow cytometric abnormalities ≥3 were present in proven-MDS (n = 23) with a sensitivity and specificity of 78 % and 94 %, respectively, as per Ogata score. The addition of CD38 MFI to the score yielded sensitivity and specificity of 82 % and 88 %, respectively. Additional analysis of aberrant expression of CD15, CD11b, and CD56 increased the diagnostic power of the FCM score. A qualitative analysis of data also showed differences in maturation patterns in proven-MDS compared to the control group.

CONCLUSION

Single tube 10-color FCM scoring, including Ogata score, modified-FCM scores, and radar plots pattern analysis, showed significant abnormalities in proven-MDS cases in this pilot study. Large databases, including FCM-scoring and pattern-based analysis for normal BM maturation, could be further validated and standardized for screening MDS.

Pretreatment CD34+/CD38- Cell Burden as Prognostic Factor in Myelodysplastic Syndrome Patients Receiving Allogeneic Stem Cell Transplantation

Myelodysplastic syndrome (MDS) is a highly heterogeneous clonal hematopoietic disorder. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative treatment and is of particular interest in patients at high risk for progression to acute myeloid leukemia (AML). In MDS, CD34⁺/CD38^- cells possess MDS stem cell potential, and secondary AML (sAML) clones originate from the MDS disease stage. However, the prognostic impact of the pretreatment stem cell population burden in MDS remains unknown. We retrospectively analyzed the prognostic impact of the pretreatment CD34⁺/CD38^- cell burden in 124 MDS patients who received allogeneic HSCT at our institution. A high pretreatment bone marrow CD34⁺/CD38^- cell burden (≥1%) was associated with worse genetic risk and a higher incidence of blast excess. Patients with a high CD34⁺/CD38^- cell burden had a significantly higher cumulative incidence of MDS relapse, a higher cumulative incidence of secondary AML, and a trend for shorter overall survival after allogeneic HSCT. In multivariable analyses this prognostic impact was shown to be independent of other clinical and cytogenetic risk factors in MDS. Patients suffering MDS relapse or progression to AML also had a higher pre-treatment CD34⁺/CD38^- cell burden as a continuous variable. The observed prognostic impact is likely mediated by MDS stem cells within the CD34⁺/CD38^- cell population initiating MDS relapse or progression to AML. New therapeutic strategies targeting MDS stem cells might improve outcomes.

An increased percentage of myeloid CD34+ bone marrow cells stratifies intermediate IPSS-R myelodysplastic syndrome patients into prognostically significant groups

INTRODUCTION

The Revised International Prognostic Scoring System (IPSS-R) for myelodysplastic syndromes (MDS) has established an intermediate category where a disease-modifying intervention is a matter of debate. Flow cytometry allows us to determine a fraction of immature myeloid cells in a semiautomated procedure. The aim of this study, mirroring IPSS-R study inclusion criteria, was to test whether bone marrow (BM) CD34+My percentage has independent prognostic value in the MDS setting.

METHODS

BM CD34+My cells were quantified, at diagnosis, selecting CD34+/CD45+/CD11b±/CD13+. Patients were excluded when receiving treatment for altering the natural course of the disease and when IPSS-R could not be calculated due to the lack of metaphases. Finally, Cox analyses were performed, on a series of 260 patients, for overall survival (OS) and time to acute myeloid leukemia (AML) transformation.

RESULTS

By analyzing ROC curves, the most accurate prognostic variable, regarding blasts by cytology and CD34+ by cytometry, was the percentage of blasts by microscopy. The percentage of CD34+My in BM showed an AUC of 0.767 and 0.576 for time to AML transformation and OS, respectively. When performing a multivariate regression including the IPSS-R and the percentage of BM CD34+My cells >1%, both factors predicted for a shorter time to AML transformation. In addition, CD34+My percentage successfully stratified the intermediate IPSS-R category into two prognostic groups with a relative risk of 5.73 (95% CI [1.2-27.8]; P = .03).

CONCLUSION

We found that BM CD34+My percentage has an independent value concerning the IPSS-R, especially relevant for the prediction of transformation to AML and within the intermediate group.

Prognostic evaluation of ALIP and CD34 immunostaining in IPSS-R subgroups of myelodysplastic syndromes

In order to evaluate the prognostic value of abnormal localisation of immature precursors (ALIP) and CD34 immunostaining in myelodysplastic syndromes (MDS), bone marrow histopathological features in 187 MDS patients were retrospectively analysed and the prognostic significance of ALIP and CD34 immunostaining on overall survival (OS) and progression to leukaemia-free survival (PFS) in total patients and different Revised-International Prognostic Scoring System (IPSS-R) subgroups were evaluated. In univariate analysis, age ≥60, ALIP, ≥5% CD34+ cells, CD34+ clusters and IPSS-R subgroups were associated with shorter OS (p = 0.027, p < 0.0001, p < 0.0001, p < 0.0001, p < 0.0001, respectively) and PFS (p = 0.029, p = 0.006, p = 0.001, p < 0.0001, p < 0.0001, respectively). Haemoglobin level had a significant impact on OS (p < 0.0001) but not on PFS (p = 0.054). In multivariate analysis, ALIP, haemoglobin level, ≥5% CD34+ cells, CD34+ clusters and IPSS-R subgroups had independent influence on OS (p = 0.012, p < 0.0001, p = 0.010, p < 0.0001, p < 0.0001, respectively), while only CD34+ clusters and IPSS-R subgroups had independent influence on PFS (p < 0.0001, p = 0.016, respectively). In different IPSS-R subgroups, ALIP could maintain its prognostic impact in lower IPSS-R risk subgroups, while ≥5% CD34+ cells and CD34+ clusters had significant prognostic value in both lower and intermediate-higher IPSS-R risk subgroups. Therefore, CD34+ clusters showed more important prognostic impact on survival and progression to leukaemia.

Improving the differential diagnosis between myelodysplastic syndromes and reactive peripheral cytopenias by multiparametric flow cytometry: the role of B-cell precursors

Background

Immunophenotyping is a valuable ancillary technique for the differential diagnosis between myelodysplastic syndromes (MDS) with low bone marrow (BM) blast counts and a normal karyotype, and reactive peripheral (PB) cytopenias. Our aim was to search for the most important variables for this purpose. We also analyzed the age variation of BM B-cell precursors (BCP) and its differences in reactive and clonal cytopenias.

Methods

Immunophenotypic analyzes were performed in BM of 54 patients with MDS (76% with BM blasts <5%) and 35 cases of reactive cytopenias. Healthy allogeneic BM transplantation donors (n = 41) were used as controls. We used a four-color panel of antibodies analyzing 9 granulocytic, 8 monocytic and 6 CD34⁺ cell features.

Results

Asynchronous shift to the left in maturing granulocytes and increase in CD16⁺ monocytes were also found in reactive PB cytopenias, but the most important aberrancies in MDS were seen in myeloid CD34⁺ cells. Decrease in BCP, that is a hallmark of MDS, could also be found in reactive cytopenias, especially in patients >55 years. % BM BCP could be calculated by the formula: (−7.97 × log age) + (4.24 × log % CD34⁺cells) – (0.22 x nr. alterations CD34⁺cells) + 0.577. Corrected R² = 0.467.

Conclusion

Analysis of myelomonocytic precursors and CD34⁺ cells was satisfactory for the differential diagnosis between reactive PB cytopenias and MDS. The most specific alterations were found in CD34⁺ cells. Comparison of the values obtained with those of normal age-matched controls is recommended.

Revisiting guidelines for integration of flow cytometry results in the WHO classification of myelodysplastic syndromes-proposal from the International/European LeukemiaNet Working Group for Flow Cytometry in MDS

Definite progress has been made in the exploration of myelodysplastic syndromes (MDS) by flow cytometry (FCM) since the publication of the World Health Organization 2008 classification of myeloid neoplasms. An international working party initiated within the European LeukemiaNet and extended to include members from Australia, Canada, Japan, Taiwan and the United States has, through several workshops, developed and subsequently published consensus recommendations. The latter deal with preanalytical precautions, and propose small and large panels, which allow evaluating immunophenotypic anomalies and calculating myelodysplasia scores. The current paper provides guidelines that strongly recommend the integration of FCM data with other diagnostic tools in the diagnostic work-up of MDS.

Feedback signals in myelodysplastic syndromes: increased self-renewal of the malignant clone suppresses normal hematopoiesis

Myelodysplastic syndromes (MDS) are triggered by an aberrant hematopoietic stem cell (HSC). It is, however, unclear how this clone interferes with physiologic blood formation. In this study, we followed the hypothesis that the MDS clone impinges on feedback signals for self-renewal and differentiation and thereby suppresses normal hematopoiesis. Based on the theory that the MDS clone affects feedback signals for self-renewal and differentiation and hence suppresses normal hematopoiesis, we have developed a mathematical model to simulate different modifications in MDS-initiating cells and systemic feedback signals during disease development. These simulations revealed that the disease initiating cells must have higher self-renewal rates than normal HSCs to outcompete normal hematopoiesis. We assumed that self-renewal is the default pathway of stem and progenitor cells which is down-regulated by an increasing number of primitive cells in the bone marrow niche – including the premature MDS cells. Furthermore, the proliferative signal is up-regulated by cytopenia. Overall, our model is compatible with clinically observed MDS development, even though a single mutation scenario is unlikely for real disease progression which is usually associated with complex clonal hierarchy. For experimental validation of systemic feedback signals, we analyzed the impact of MDS patient derived serum on hematopoietic progenitor cells in vitro: in fact, MDS serum slightly increased proliferation, whereas maintenance of primitive phenotype was reduced. However, MDS serum did not significantly affect colony forming unit (CFU) frequencies indicating that regulation of self-renewal may involve local signals from the niche. Taken together, we suggest that initial mutations in MDS particularly favor aberrant high self-renewal rates. Accumulation of primitive MDS cells in the bone marrow then interferes with feedback signals for normal hematopoiesis – which then results in cytopenia.

Myelodysplastic syndromes are diseases which are characterized by ineffective blood formation. There is accumulating evidence that they are caused by an aberrant hematopoietic stem cell. However, it is yet unclear how this malignant clone suppresses normal hematopoiesis. To this end, we generated mathematical models under the assumption that feedback signals regulate self-renewal and proliferation of normal and diseased stem cells. The simulations demonstrate that the malignant cells must have particularly higher self-renewal rates than normal stem cells – rather than higher proliferation rates. On the other hand, down-regulation of self-renewal by the increasing number of malignant cells in the bone marrow niche can explain impairment of normal blood formation. In fact, we show that serum of patients with myelodysplastic syndrome, as compared to serum of healthy donors, stimulates proliferation and moderately impacts on maintenance of hematopoietic stem and progenitor cells in vitro. Thus, aberrant high self-renewal rates of the malignant clone seem to initiate disease development; suppression of normal blood formation is then caused by a rebound effect of feedback signals which down-regulate self-renewal of normal stem and progenitor cells as well.

Diagnostic potential of CD34+ cell antigen expression in myelodysplastic syndromes

The World Health Organization introduced flow cytometry as an additional criterion for diagnosis of myelodysplastic syndromes (MDS). Aberrant antigen expression on bone marrow (BM) blasts may identify "low-grade MDS." This study aimed to examine differences in antigen expression on CD34+ BM cells between patients with MDS and those with secondary cytopenia. BM aspirates of 175 patients with cytopenia were classified as MDS or secondary cytopenia. Expression of stem cell antigens (CD34, CD133), myeloid antigens (CD13, CD33), B-cell antigens (CD19, CD10), growth factor receptors (CD117, CD123), and chemokine receptor (CD184) was examined. Thirty-two normal adults and 49 patients with CD34+ acute myeloid leukemia (AML) were also examined. High percentage of CD34+ cells, CD117 and CD123 overexpression, and abnormal CD45 expression on these cells are the best markers for MDS. These phenotypic aberrancies correlate with number of blasts and degree of dysplasia, and were similar to those in CD34+ AML, thus reflecting the relationship between these disorders.

Evaluation of flow cytometric assessment of myeloid nuclear differentiation antigen expression as a diagnostic marker for myelodysplastic syndromes in a series of 269 patients

BACKGROUND

Myeloid nuclear differentiation antigen (MNDA) is expressed in myelomonocytic cells with highest levels in mature granulocytes and monocytes. It is suggested to be expressed more weakly in patients with myelodysplastic syndromes (MDS). The analysis of MNDA therefore may improve diagnostic capabilities of multiparameter flow cytometry (MFC) in MDS.

METHODS

We used MFC for detection of MNDA expression in 269 patients with suspected or known MDS, acute myeloid leukemia (AML) or chronic myelomonocytic leukemia (CMML), cytopenia of unknown cause or without malignancy (negative controls). Results were compared with the diagnoses revealed by cytomorphology (CM) and cytogenetics (CG).

RESULTS

Percentages of granulocytes and monocytes with diminished MNDA expression (dimG and dimM) were higher in patients with MDS (mean ± SD, 20% ± 20%, P < 0.001 and 31% ± 24%, P < 0.001) and AML (27% ± 27%, P = 0.007 and 45% ± 31%, P = 0.001) diagnosed by CM, vs. patients without MDS (8% ± 10% and 16% ± 11%), respectively. Significant differences were also found for mean fluorescence intensity (MFI) of MNDA in monocytes which was lower in MDS (mean ± SD, 71 ± 36, P = 0.004) and AML (55 ± 39, P < 0.001) vs. no MDS samples (85 ± 28), respectively. Within patients with MDS, cases with cytogenetic aberrations showed a trend to higher %dimG (24% ± 18%, P = 0.083) compared with those without (16% ± 21%). Cut-off values for %dimG (12%) and %dimM (22%) as well as for MFI in monocytes (72) were defined capable of discriminating between MDS and non-MDS.

CONCLUSION

MNDA expression in bone marrow cells can be assessed reliably by MFC and may facilitate evaluation of dyspoiesis when added to a standard MDS MFC panel.

Standardization of flow cytometry in myelodysplastic syndromes: a report from an international consortium and the European LeukemiaNet Working Group

Flow cytometry (FC) is increasingly recognized as an important tool in the diagnosis and prognosis of myelodysplastic syndromes (MDS). However, validation of current assays and agreement upon the techniques are prerequisites for its widespread acceptance and application in clinical practice. Therefore, a working group was initiated (Amsterdam, 2008) to discuss and propose standards for FC in MDS. In 2009 and 2010, representatives from 23, mainly European, institutes participated in the second and third European LeukemiaNet (ELN) MDS workshops. In the present report, minimal requirements to analyze dysplasia are refined. The proposed core markers should enable a categorization of FC results in cytopenic patients as 'normal', 'suggestive of', or 'diagnostic of' MDS. An FC report should include a description of validated FC abnormalities such as aberrant marker expression on myeloid progenitors and, furthermore, dysgranulopoiesis and/or dysmonocytopoiesis, if at least two abnormalities are evidenced. The working group is dedicated to initiate further studies to establish robust diagnostic and prognostic FC panels in MDS. An ultimate goal is to refine and improve diagnosis and prognostic scoring systems. Finally, the working group stresses that FC should be part of an integrated diagnosis rather than a separate technique.